overlay_dialog: Add an overlay text dialog that accepts controller input

An OverlayDialog is an interactive dialog that accepts controller input (while a game is running)
This dialog attempts to replicate the look and feel of the Nintendo Switch's overlay dialogs and
provide some extra features such as embedding HTML/Rich Text content in a QTextBrowser.
The OverlayDialog provides 2 modes: one to embed regular text into a QLabel and another to embed
HTML/Rich Text content into a QTextBrowser.

Co-authored-by: Its-Rei <kupfel@gmail.com>