Impl Write on text buffers

[ranfdev]

Text is always written at the end. I could insert the text at cursor position, but I think inserting always at the end provides more consistent behavior.

[ranfdev]

I wanted to implement it also over IsA<Editable> but I'm unable to, because of rust's restrictions on doing blanked implementations of foreign traits.

Nevermind, I'll settle for implementing this on text buffers.

[bilelmoussaoui]

I wanted to implement it also over IsA<Editable> but I'm unable to, because of rust's restrictions on doing blanked implementations of foreign traits.

Nevermind, I'll settle for implementing this on text buffers.

You could at least implement it for the provided Editables like Entry/Text ? Not sure if that is a good idea anyway

[ranfdev]

Well I could, but the user can also call entry.buffer() and then use Write on that, so... We aren't missing much anyway.

This also keeps things consistent with libadwaita. I'm not going to implement Write on the adw's Editable's.