Added plugin support.
Plugin structure:
- main(): performed continuously, but with a delay in checks.
- start(): executed once when the program is started.
- exit(): executed once when exiting the program.
- active(): performed continuously when the PC is in active mode.
- afk(): performed continuously when the PC is in afk mode.
- pause(): performed continuously when the PC is in pause mode.
- afk_enter(): executed every time the PC goes into idle mode.
- afk_exit(): executed every time the PC goes into active mode.