Fix：修复拖拽画布和拖拽调整图片时会选中文字的问题

simple-mind-map/src/core/view/View.js

@@ -29,8 +29,9 @@ class View {
       this.fit()
     })
     // 拖动视图
-    this.mindMap.event.on('mousedown', () => {
+    this.mindMap.event.on('mousedown', e => {
       if (this.mindMap.opt.isDisableDrag) return
+      e.preventDefault()
       this.sx = this.x
       this.sy = this.y
     })

simple-mind-map/src/plugins/NodeImgAdjust.js

@@ -154,6 +154,7 @@ class NodeImgAdjust {
     })
     btnEl.addEventListener('mousedown', e => {
       e.stopPropagation()
+      e.preventDefault()
       this.onMousedown(e)
     })
     btnEl.addEventListener('mouseup', e => {