Add new entries under 'Recent News': 'Urgent' and 'Community' and remove 'Announcements'

Closes #1025

See merge request !1215

LICENSE: Update copyright notice

See merge request !1226

Fix broken meta tags (description, og:title, og:description)

Closes #925

See merge request !1216

Fix broken 'next' and 'prev' in 'all posts'

Closes #1047

See merge request !1213

Add mobile-specific CSS for selector in Merchants page

Closes #1044

See merge request monero-project/monero-site!1209

fix broken 'Mining' page

Closes #1052

See merge request !1220

5 new merchants + edited 'InstaEx

Closes #1046, #1043, #1036, #1038, #1037, and #975

See merge request !1214

Remove 'langs' from language files and move them to their own 'languages.yml' file in /_data

See merge request monero-project/monero-site!1212

en.yml: remove obsolete 'ffs' keys

See merge request !1211

Remove 'untranslated' snippet logic from all pages (except where it's called using 'include')

See merge request !1210

Add note about removal of long PIDs

Closes #1024

See merge request !1191

footer: use variable instead of absolute link for RSS feed

See merge request !1180

zh-tw, zh-cn, tr, nl and ar are untranslated

and add 'untranslated' snippet where needed

The Urgent tag is meant to show prioritary communications that the community should be aware of as soon as possible
'Community' will show all non-urgent communications and general blog posts

- NOWPayments
- Rexi
- Minko
- SideShift
- Bidali
- Edited InstaEx

The list of languages doesn't need to be translated, so there is no reason to keep it in the language files. Moved to its own
file (/_data/languages.yml). Now the language dropdown parses the languages from there.
This change is also needed for the migration to Weblate (which would ask translators to translate the language names).

It's not compatible with Weblate and will be not needed after the migration

main: add "Reasonably" before "Private"

See merge request !1136

Add hash to point writeup

See merge request !1205

Remove mention of '/r/moneromining'

See merge request !1195

-hash to point writeup from Shen Noether: add to MRL Research page as unpublished paper [use summary instead of abstract]
-fixed formatting issue with MRL-0005

fix conflict with added Triptych paper

Delete index.md.orig

Add blog post on supply auditability

See merge request !1208

Update README.md

See merge request !1206

translating to russian language (update 'download page' and new strings)

See merge request monero-project/monero-site!1204

Remove duplicate 'copyright' key from all languages

See merge request monero-project/monero-site!1203

gitlab-ci: fix UTF-8 support

See merge request !1201

Deactivate 'upgrade' banner

See merge request !1199

Triptych paper

See merge request !1197

Cleanup of the 'Merchants' Page

Closes #1032

See merge request !1194

Library: Add link to masteringmonero.com and remove preview

Closes #1012

See merge request !1193