config/qa-checks: Enable inclusivity check

Enable inclusivity check in qa-checks to enhance spell check.
As the word 'master' is a forbidden word in the inclusivity check, so
update the documentation to ignore it in the specific places with the
'inclusivity-exception' keyword.

Issue-Id: SCM-4874
Signed-off-by: Robbie Cao <robbie.cao@arm.com>
Change-Id: I809001453ad07dcc47d3260dc8ee203e6741d1e0