Add fuzzing setup for `Message::decode` #195

Job	Run time
Check spelling	1m 7s
Check dependencies (ubuntu-latest)	3m 42s
Integration tests (ubuntu-latest)	46s
Check formatting (ubuntu-latest)	1m 9s
Check dependencies (macos-latest)	4m 17s
Integration tests (macos-latest)	58s
Check formatting (macos-latest)	3m 4s
Clippy lints (ubuntu-latest)	1m 16s
Check dependencies (windows-latest)	4m 4s
Integration tests (windows-latest, true)	2m 33s
Check formatting (windows-latest)	3m 4s
Clippy lints (macos-latest)	3m 14s
Clippy lints (windows-latest)	3m 38s
Unit tests (ubuntu-latest)	1m 25s
Unit tests (macos-latest)	1m 59s
Unit tests (windows-latest)	3m 53s
	40m 9s

Provide feedback