use `core.getBooleanInput()` to retrieve boolean input values

[gr2m]

Right now we core.getInput() and parse it with Boolean(). I learned that @actions/core now has a dedicated method for it.

create-github-app-token/main.js

Lines 33 to 35 in f577941

	const skipTokenRevoke = Boolean(
	core.getInput("skip-token-revoke") || core.getInput("skip_token_revoke")
	);