stable/13: README.md MFCs; README removal

[mhorne]

Summary

Catch stable/13 up to changes in main. The continued existence of both README and README.md can be confusing.

Reported by: pauamma

This includes the following commits:

readme: update style

Update the style to one sentence per line, as is currently used in the FreeBSD
document project. Make the links to the handbook clickable.

(cherry picked from commit 2918e9fdb82ffe5e95cab90a754bc6c2b6dd16a2)

Fix arch rendering

(cherry picked from commit dbd92cc2a4915a2070c93cff423314f43edfc841)

readme: Link to COPYRIGHT file

(cherry picked from commit e75eac2cb81c510389f527da14cec4a16123e673)

Update doc links in README

(cherry picked from commit cada2b74b8d670741643dca8e3d40c39d8fc7105)

Whitespace cleanup

(cherry picked from commit aaf998056ed46c0dfb429e3e5cfe624c8aa4dec8)

Remove README in favor of README.md

Complete the transition to README.md I started 3 years ago. Remove the
now-redundant README file. It's currently just README.md w/o the light markup
and adds no real value. This also allows us to use additional MarkDown
markup as we see fit w/o worrying about keeping things in sync.

(cherry picked from commit 8a157722e947191a63e9108cbfb60ee2605858b4)

[lwhsu]

I don't think this MFC really needs approval from core, as it's syncing from the main branch.

[jhb]

That said, fire away.

[mhorne]

In D37327#848541, @lwhsu wrote:

I don't think this MFC really needs approval from core, as it's syncing from the main branch.

Indeed, it was a regex match on "GNU General Public License" that added Core as a reviewer.

[imp]

In D37327#848801, @mhorne wrote:

In D37327#848541, @lwhsu wrote:

I don't think this MFC really needs approval from core, as it's syncing from the main branch.

Indeed, it was a regex match on "GNU General Public License" that added Core as a reviewer.

If it were me, I wouldn't have waited :)

core@ already approved it going into head, so separate approval isn't needed unless there's some
material difference. If in the unlikely event it's wrong, core@ can back it out. :)