Parse --output from --args similar to --format?

[mre]

In #198 it was discovered that --output is ignored when used inside args. We might want to add a similar workaround as for --format:

lychee-action/entrypoint.sh

Lines 18 to 22 in 5a5fc0b

	ARGS="${INPUT_ARGS}"
	FORMAT=""
	# Backwards compatibility:
	# If `format` occurs in args, ignore the value from `INPUT_FORMAT`
	[[ "$ARGS" =~ "--format " ]] || FORMAT="--format ${INPUT_FORMAT}"

This way, users cannot run into a similar situation anymore. The alternative is to print a warning instead and show how to correctly set the output parameter.