refactor: Swtich `Shortcut::steam_id` from a field to a method #160

Job	Run time
wasm	30s
validation (ubuntu-latest, stable)	26s
validation (ubuntu-latest, beta)	40s
validation (macos-latest, stable)	18s
validation (macos-latest, beta)	57s
validation (windows-latest, stable)	2m 3s
validation (windows-latest, beta)	1m 24s
	6m 18s

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