docs: hacking: emphasize some sections
docs: hacking: emphasize some sections

Namely:
* holding up the first-time patch submissions for moderation,
  which might cause first-time submitters to question the process
* not CC-ing individual developers

Signed-off-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Reviewed-by: Daniel P. Berrangé <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>
Reviewed-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>

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