doc: Add first version of code of conduct

As a starting point, copying coreboot's one in the absence
of our own.
coreboot's CoC exists for some time and is known to work, so
it's a good starting point. We can iterate on this and make
upgrades and amendments that make sense for flashrom community.
Meanwhile we can share code of conduct with coreboot. We
do have the same servers and infrastructure anyway.

Change-Id: Icd82ba79687da3a2698d84f5cbfe824fbab0c426
Signed-off-by: Anastasia Klimchuk <aklm@flashrom.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/78203
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

doc/about_flashrom/index.rst

@@ -5,3 +5,4 @@ About flashrom
     :maxdepth: 1
 
     team
+    code_of_conduct