Adding Move Line Shortcuts to the Editor

[J3ekir]

I think it would be a nice feature. I tried a pull request, but failed.

[Yuki2718]

PR is restricted for those who have contribution history.

[kaya51]

A nice feature. I sort them too, not too often though.

I don't think Raymond will add this. We'll get it when he switches to CodeMirror 6.