docs(contribution-guidelines): updated the build configuration section

Added a couple of sub-sections (Coverity Scan and Test Configuration)
under "Add build configuration" to update the patch owners on the
sections they need to be aware of while introducing new source files.

Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
Change-Id: I84adb182f9633863aac864df43578249c2269c1e
1 file changed