Add a preference item for the Marked 2 application path

The preference has no default. On extension launch, if it isn’t set, or the path it is set to doesn’t exist, then do a discovery by bundle ID. If multiple versions are found, rank:

• Newer wins over older
• Setapp wins over non-Setapp
• non-App Store wins over non-App Store

Correct repository links

v1.0.2

Correct repository links

Readme correction

v1.0.1

Correct readme after updating icon

Initial release

v1.0

Marked 2 icons