chore: add vant-touch-emulator package

packages/vant-touch-emulator/README.md

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+# Vant Touch Emulator
+
+在桌面端上模拟移动端 touch 事件，实现方式来自于 [hammerjs/touchemulator](https://github.com/hammerjs/touchemulator).
+
+## 安装
+
+```bash
+npm i @vant/touch-emulator -S
+```
+
+## 使用指南
+
+直接在代码中引入模块即可，模块会自动完成初始化并生效
+
+```js
+import '@vant/touch-emulator';
+```
+
+## CDN 引入
+
+```html
+<script src="https://cdn.jsdelivr.net/npm/@vant/touch-emulator"></script>
+```

packages/vant-touch-emulator/index.js

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+/* eslint-disable */
+/**
+ * Emulate touch event
+ * Source：https://github.com/hammerjs/touchemulator
+ */
+
+var eventTarget;
+var supportTouch = 'ontouchstart' in window;
+
+// polyfills
+if (!document.createTouch) {
+  document.createTouch = function(view, target, identifier, pageX, pageY, screenX, screenY) {
+    // auto set
+    return new Touch(target, identifier, {
+      pageX: pageX,
+      pageY: pageY,
+      screenX: screenX,
+      screenY: screenY,
+      clientX: pageX - window.pageXOffset,
+      clientY: pageY - window.pageYOffset
+    }, 0, 0);
+  };
+}
+
+if (!document.createTouchList) {
+  document.createTouchList = function() {
+    var touchList = TouchList();
+    for (var i = 0; i < arguments.length; i++) {
+      touchList[i] = arguments[i];
+    }
+    touchList.length = arguments.length;
+    return touchList;
+  };
+}
+
+/**
+ * create an touch point
+ * @constructor
+ * @param target
+ * @param identifier
+ * @param pos
+ * @param deltaX
+ * @param deltaY
+ * @returns {Object} touchPoint
+ */
+
+var Touch = function Touch(target, identifier, pos, deltaX, deltaY) {
+  deltaX = deltaX || 0;
+  deltaY = deltaY || 0;
+
+  this.identifier = identifier;
+  this.target = target;
+  this.clientX = pos.clientX + deltaX;
+  this.clientY = pos.clientY + deltaY;
+  this.screenX = pos.screenX + deltaX;
+  this.screenY = pos.screenY + deltaY;
+  this.pageX = pos.pageX + deltaX;
+  this.pageY = pos.pageY + deltaY;
+};
+
+/**
+ * create empty touchlist with the methods
+ * @constructor
+ * @returns touchList
+ */
+function TouchList() {
+  var touchList = [];
+
+  touchList['item'] = function(index) {
+    return this[index] || null;
+  };
+
+  // specified by Mozilla
+  touchList['identifiedTouch'] = function(id) {
+    return this[id + 1] || null;
+  };
+
+  return touchList;
+}
+
+/**
+ * Simple trick to fake touch event support
+ * this is enough for most libraries like Modernizr and Hammer
+ */
+function fakeTouchSupport() {
+  var objs = [window, document.documentElement];
+  var props = ['ontouchstart', 'ontouchmove', 'ontouchcancel', 'ontouchend'];
+
+  for (var o = 0; o < objs.length; o++) {
+    for (var p = 0; p < props.length; p++) {
+      if (objs[o] && objs[o][props[p]] === undefined) {
+        objs[o][props[p]] = null;
+      }
+    }
+  }
+}
+
+/**
+ * only trigger touches when the left mousebutton has been pressed
+ * @param touchType
+ * @returns {Function}
+ */
+function onMouse(touchType) {
+  return function(ev) {
+    // prevent mouse events
+
+    if (ev.which !== 1) {
+      return;
+    }
+
+    // The EventTarget on which the touch point started when it was first placed on the surface,
+    // even if the touch point has since moved outside the interactive area of that element.
+    // also, when the target doesnt exist anymore, we update it
+    if (ev.type === 'mousedown' || !eventTarget || eventTarget && !eventTarget.dispatchEvent) {
+      eventTarget = ev.target;
+    }
+
+    triggerTouch(touchType, ev);
+
+    // reset
+    if (ev.type === 'mouseup') {
+      eventTarget = null;
+    }
+  };
+}
+
+/**
+ * trigger a touch event
+ * @param eventName
+ * @param mouseEv
+ */
+function triggerTouch(eventName, mouseEv) {
+  var touchEvent = document.createEvent('Event');
+  touchEvent.initEvent(eventName, true, true);
+
+  touchEvent.altKey = mouseEv.altKey;
+  touchEvent.ctrlKey = mouseEv.ctrlKey;
+  touchEvent.metaKey = mouseEv.metaKey;
+  touchEvent.shiftKey = mouseEv.shiftKey;
+
+  touchEvent.touches = getActiveTouches(mouseEv);
+  touchEvent.targetTouches = getActiveTouches(mouseEv);
+  touchEvent.changedTouches = createTouchList(mouseEv);
+
+  eventTarget.dispatchEvent(touchEvent);
+}
+
+/**
+ * create a touchList based on the mouse event
+ * @param mouseEv
+ * @returns {TouchList}
+ */
+function createTouchList(mouseEv) {
+  var touchList = TouchList();
+  touchList.push(new Touch(eventTarget, 1, mouseEv, 0, 0));
+  return touchList;
+}
+
+/**
+ * receive all active touches
+ * @param mouseEv
+ * @returns {TouchList}
+ */
+function getActiveTouches(mouseEv) {
+  // empty list
+  if (mouseEv.type === 'mouseup') {
+    return TouchList();
+  }
+  return createTouchList(mouseEv);
+}
+
+/**
+ * TouchEmulator initializer
+ */
+function TouchEmulator() {
+  fakeTouchSupport();
+
+  window.addEventListener('mousedown', onMouse('touchstart'), true);
+  window.addEventListener('mousemove', onMouse('touchmove'), true);
+  window.addEventListener('mouseup', onMouse('touchend'), true);
+}
+
+// start distance when entering the multitouch mode
+TouchEmulator['multiTouchOffset'] = 75;
+
+if (!supportTouch) {
+  new TouchEmulator();
+}

packages/vant-touch-emulator/package.json

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+{
+  "name": "@vant/touch-emulator",
+  "version": "1.1.0",
+  "description": "Vant touch emulator",
+  "main": "index.js",
+  "scripts": {
+    "release": "npm publish --access publish"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/youzan/vant.git",
+    "directory": "packages/vant-touch-emulator"
+  },
+  "keywords": [
+    "vant"
+  ],
+  "author": "neverland",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/youzan/vant/issues"
+  },
+  "homepage": "https://github.com/youzan/vant/packages/vant-touch-emulator#readme"
+}