[L] Change in flashrom[main]: doc: Convert serprog docs to rst and add to doc directory

[Anastasia Klimchuk (Code Review)]

Attention is currently required from: Riku Viitanen, Swift Geek (Sebastian Grzywna), Sydney, Thomas Heijligen, Urja Rannikko.

Anastasia Klimchuk has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/82018?usp=email )

Change subject: doc: Convert serprog docs to rst and add to doc directory
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Patch Set 1:

(1 comment)

Patchset:

PS1: 
I tried to gather people who know about serprog, or did development recently.
One person I was not able to contact is GNUtoo, if someone knows how to contact them and invite to review, that would be great!

Many thanks for review!

I have converted existing docs to rst format, fixed few typos and removed broken links. Otherwise, it's the same content.