Improve external buffers

[asvetliakov]

Custom editors/view can be used for them to prevent messing with normal editors

Related:

#476
#459
#294
#211

[micimize]

Cross posting my thinking on this from #288 (comment), layout-wise:

I think a really good approach to multiple buffers (#505) might lead to the most optimal, fully-featured command buffer. Maybe something leveraging horizontal splits. View: Toggle Split Editor In Group and View: Toggle Layout of Split Editor in Group can be used to make "borderless" splits of the same file, and microsoft/vscode#36700 (comment) implies there might be a way to do that using some custom view.