Add fuzzing setup for `Message::decode` #194

Job	Run time
Check spelling	1m 5s
Unit tests (ubuntu-latest)	1m 36s
Check formatting (ubuntu-latest)	1m 9s
Check formatting (macos-latest)	3m 27s
Unit tests (macos-latest)	1m 58s
Check dependencies (ubuntu-latest)	3m 54s
Check formatting (windows-latest)	2m 25s
Unit tests (windows-latest)	3m 36s
Check dependencies (macos-latest)	6m 51s
Integration tests (ubuntu-latest)	43s
Check dependencies (windows-latest)	8m 28s
Integration tests (macos-latest)	2m 10s
Clippy lints (ubuntu-latest)	1m 32s
Integration tests (windows-latest, true)	2m 14s
Clippy lints (macos-latest)	1m 50s
Clippy lints (windows-latest)	3m 44s
	46m 42s

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