Currently the commit message validation tool from `ng-dev` validates
the `BREAKING CHANGE:` commit message notes. This commit adds a similar
check for `DEPRECATED:` commit message notes.
Additionally, the check for breaking changes is reworked slightly to
be more tolerant (i.e. if there is only a single line break after the
summary; this is acceptable as per the parser and commonly done in the
COMP repo). The checks have been updated to capture wrong keywords that
are commonly used instead of the correct one. e.g. if a commit message
uses `DEPRECATIONS:` instead of `DEPRECATED:`, the validation will fail.
This prevents changelog generation issues where breaking change notes,
or deprecations are missing. This happened in the COMP repo where
the `DEPRECATED:` keyword was used incorrectly. See:
https://github.com/angular/components/commit/99391e79391d20c6ef2f95a3ea4fd6901dcb631d
PR Close#42436
Paul Gschwendtner
bc5a8f4d37