Previously, when creating the archive feed September 2022, it linked to
itself. That is clearly wrong since it obviously should have linked to
August 2022 instead.

Yeah, this will only work for Lyse. Sorry.

When a root twt doesn't have any known replies the URLs view didn't
provide an URL for the conversation on twtxt.net. Now it will always
generate it, so users can quickly jump over to the yarnd web UI.

Big thanks to fastidious over at
https://arrakis.netbros.com/user/fastidious/twtxt.txt for bringing up
this idea!

Usually it doesn't matter if the mentions are preceding the subject or
not. But lately I had the situations that it was more convenient to have
the subject at the very front, so it's easier to reply to all of the
mentions without moving around the text. Let's illustrate this on the
following example. Previously a reply template would look like this:

  @<hugo https://example.com/twtxt.txt> @<cathy https://example.org/twtxt.txt> (#abcdefg)

Now the order is reversed:

  (#abcdefgh) @<hugo https://example.com/twtxt.txt> @<cathy https://example.org/twtxt.txt>

So it's much easier to reply to both individually like that:

  (#abcdefgh) Oh great, @<hugo https://example.com/twtxt.txt>! @<cathy https://example.org/twtxt.txt>, exactly, that's what I was thinking too.

Text just has to be inserted in the middle without reordering subject
and mentions manually. Keep in mind that the subject can only be
preceded by mentions according to the Twt Subject Extension
(https://dev.twtxt.net/doc/twtsubjectextension.html), but no other
non-whitespace text.