Initial commit of swayidle
Initial commit of swayidle, for use with the Sway window manager.
Partially resolves T9396
Test Plan: - Un-comment swayidle lines in the default sway config, confirm swayidle successfully calls swaylock.
Reviewers: Triage Team, JoshStrobl
Reviewed By: Triage Team, JoshStrobl
Maniphest Tasks: T9396
Differential Revision: https://dev.getsol.us/D10283