Feat：阻止mousedown、mousemove、drag、node_mousedown事件的默认行为

simple-mind-map/src/core/event/Event.js

@@ -99,6 +99,7 @@ class Event extends EventEmitter {
 
   //  鼠标按下事件
   onMousedown(e) {
+    e.preventDefault()
     // 鼠标左键
     if (e.which === 1) {
       this.isLeftMousedown = true
@@ -114,6 +115,7 @@ class Event extends EventEmitter {
 
   //  鼠标移动事件
   onMousemove(e) {
+    e.preventDefault()
     let { useLeftKeySelectionRightKeyDrag } = this.mindMap.opt
     this.mousemovePos.x = e.clientX
     this.mousemovePos.y = e.clientY

simple-mind-map/src/core/render/node/Node.js

@@ -515,6 +515,7 @@ class Node {
       this.active(e)
     })
     this.group.on('mousedown', e => {
+      e.preventDefault()
       const {
         readonly,
         enableCtrlKeyNodeSelection,