1. Our textarea already has some editor-like feature like tab
indentation, so I thought why not also add insertion of matching closing
quotes/brackets over selected text. This does that.
2. `textareaInsertText` is replaced with `replaceTextareaSelection`
which does the same but create a new edit history entry in the textarea
so CTRL-Z works. The button that inserts tables into the textarea can
now also be reverted via CTRL-Z, which was not possible before.