FR: Add TextEditor::Listener::textEditorFocusGained

I’m not totally sure why there’s not a paired up focus gain/loss idiom here already!

It seems relatively straightforward to implement.

Just hit this one so same thought here.

I think this one’s pretty straightforward to do so here’s an example of how it could be done:

juce_TextEditor.cpp (80.8 KB)
juce_TextEditor.h (34.5 KB)