Dragging selection does not work in IE11

[suchun0]

Version

v1.3.0

Test Environment

OS: Windows 10
Browser: IE11

Current Behavior

https://nhnent.github.io/tui.editor/api/latest/tutorial-example01-basic.html

1. Place the cursor at the selection staring point.
2. Try dragging to make a selection.
3. Can figure out dragging selection does not work

Expected Behavior

• Dragging selection correctly work

[sohee-lee7]

The cause for this issue is registered in the CodeMirror issue. (codemirror/codemirror5#5759)

[sohee-lee7]

The history is too old to find out why calls refresh in focus event handler of CodeMirror. And I did not have any problems when I changed the focus event to not call refresh. I also heard from the CodeMirror maintainer that the refresh is expensive and is not a good call to the focus event. So I will change it to not call refresh.