Show a warning annotation when "master" branch usage is detected #574

Job	Run time
Code coverage (codecov)	31s
CI test (make validate)	32s
Build moodle-plugin-ci.phar	39s
Integration tests (8.3, main)	6m 18s
Integration tests (8.2, MOODLE_403_STABLE)	6m 6s
Integration tests (8.2, MOODLE_402_STABLE)	5m 39s
Integration tests (8.1, MOODLE_401_STABLE)	7m 4s
Integration tests (8.0, MOODLE_400_STABLE)	6m 28s
Integration tests (8.0, MOODLE_311_STABLE)	6m 3s
Integration tests (7.4, MOODLE_39_STABLE)	5m 49s
Integration tests (PHAR) (8.3, main)	6m 25s
Integration tests (PHAR) (8.2, MOODLE_403_STABLE)	5m 40s
Integration tests (PHAR) (8.1, MOODLE_402_STABLE)	5m 25s
Integration tests (PHAR) (8.0, MOODLE_401_STABLE)	6m 27s
Integration tests (PHAR) (7.4, MOODLE_400_STABLE)	5m 45s
	1h 14m 51s

Provide feedback