27.1; add libera chat to ERC

[Corwin Brust]

Hi Emacs Maintainers &thanks,

A new IRC network was recently created expressly for development of Free
(or also, *boo, hiss* open-source ;) software.

Can we add this patch to make ERC able to connect to this new network
available to users "out of the box"?

Here is a similar request for HexChat:
https://github.com/hexchat/hexchat/pull/2566/files

I don't see any reason we would hurry to apply this.  While I do expect
the new network to be 'around for the future', I also think those most
affected of "our users" (e.g. using IRC heavily, and for developing
free software)
are likely aware.  It would be very nice to have with the next major release
(meaning 28 and not anything 27.x).

I haven't completed my assignment paperwork (ug, someday soon, I hope).
Hopefully this qualifies as a "tiny change".  In any case, it *seems* trivial
enough.

I didn't make any news entry for the attached "starter" patch; it
would probably warrant one.

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emacs_erc_add_libera.patch
Description: Binary data