Allow to manually resize the TextEditor widget

[maximlt]

The TextEditor widget should allow an app visitor to resize it manually. The use case motivating this feature request is to be able to extend vertically the widget when the text being written/edited gets too long and no longer fits entirely in the widget.

A drag handle should be added to the widget, as is available in a standard textarea HTML element:

[hoxbro]

I was looking into this and stumbled on this thread slab/quill#3359. About how quill.js (which TextEditor is based on) is no longer supported.

It seems that Summernote could be a good alternative. Which have the option to resize vertically build-in.

[maximlt]

The fact that it is no really supported right now is unfortunate, but I think it doesn't necessarily mean that we shouldn't use it. It seems to be still very much used by people, it has really value. Yet, if there's no way to resize the table, or we have to do a super weird thing that is going to be prone to break easily, then I guess that's a valid reason to change!

I haven't had a look around to see what other libraries we could use, Summernote looks like a potential candidate if we need to change.

@philippjfr what do you think?