tools/qa-checks: Add spell_check module

This patch adds the spell_check module that checks all files within the target
paths for spelling errors. To support this, a custom EWAOL dictionary is
provided that extends the standard language dictionary with additional
permitted words.

Issue-Id: SCM-2585
Signed-off-by: Richard Neill <richard.neill@arm.com>
Change-Id: I07780a0c83e5a2840bf294764cc02acb4e96663f