Thunderbird for Android / K-9 mail: Update to reflect rebranding

Thunderbird for Android is released, as of 2024-11-12, this is
alternative version of K-9 Mail, with slightly different option
names.

Link: https://blog.thunderbird.net/2024/10/thunderbird-for-android-8-0-takes-flight/
Link: https://lists.sr.ht/~sircmpwn/public-inbox/patches/55819
Signed-off-by: Yongmin Hong <revi@omglol.email>

Use "Compose in plain text" in all cases

Out of 28 list of clients, 25 uses "Compose in plain text" and
3 uses "Compose in plaintext". Fix those 3 to match the majority
25.

Signed-off-by: Yongmin Hong <revi@omglol.email>

Fix fastmail section

Update instructions on setting plain text format in fastmail. Besides,
fastmail now supports bottom posting

Add Disroot

This commit adds information for how to configure Disroot to use plain
text email.

Instructions for bottom posting from the gmail web client

Add Posteo

This commit adds the Posteo Webmail service. Along side the guidelines there
is also a notice about the vendor lock-in. Translated to Spanish by a human.
Version 2 is just a rebase.

typo: ettiquite -> etiquette

Add Cypht to Recommended, certified list and notice

"plaintext" -> "plain text"

Credit goes to David Trudgett <DTrudgett@orange.nsw.gov.au>, who
noticed, cared and sent a malformatted patch.

Respect client name stylization

Reference RFC 1855 in section about etiquette

The commit adds a new paragraph in the etiquette section that
references the RFC document about network etiquette. Also modifies
the spanish version with text that is written by a human.

Add Roundcube to certified list and notice

Seeing the Roundcube repo, seems like roundcube by default sends only
plaintext emails with all the features properly, but the system
administrator can change the settings as they should be able to.

s/open source/free software/

Various improvements

fastmail: document text wrapping support

Signed-off-by: Vlad-Stefan Harbuz <vlad@vladh.net>

Uniquify CSS and SVG

CSS code in both HTML files is now deduplicated into a single CSS file
located at css/style.css

Same goes with the two identical SVG files, this commit only keeps one
at /assets/certified.svg

State that Geary supports bottom posting

Geary supports bottom posting, but only if you highlight the portion of
the message you want to quote. See
<https://mail.gnome.org/archives/geary-list/2016-July/msg00013.html>.

Add notmuch-emacs email client

notmuch-emacs is used by quite some kernel developers and has good
defaults for plain text.

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>

Change the link to the RFC for format=flowed

RFC 3676 says:
> Obsoletes: 2646 February 2004

Use HTTPS for www.squirrelmail.org