Re: adding src/README.md

[coypu%sdf.org@localhost]

Please consider that to write the README.md it took several revisions,
and I am doing the same for every email I send out.
Bikesheds are a hell of a burden, and phrasing is a clear bikeshed
topic: anyone can give an opinion on what color we want the words to be.
I've given detailed explanations for why some changes are bad, let's not
keep on requiring those explanations.

If I had to be concerned with ARM's trademark/branding policy, which,
depending on how objectionable my own replies sound, might require legal
counsel, it would be easier to give up.

(I don't see the point of ARM is to objecting to the 'arm64' name. It
isn't factually incorrect for us to state it, as we do actually support
ARM-designed 64bit CPUs, and it's a positive boost to their own brand.)