index.org: Tiny editing
publish.sh: Call `ox-extras-activate'
.build.yml and publish.sh: Load org-contrib/ox-extra and use it

This way headlines with an ":ignore:" tag are ignored.
Remove contribute.org and point to worg/org-contribute.html
Minor rephrasing
resources/style/org-changes.css: Use local fonts
Delete unused css files
resources/preamble.html: Remove reference to stats.orgmode.org
Replace the community button by a link to Worg

Promote some contents of the community page to the index page.
Point to the manual's installation guide

The first and most important part of install.org page was redundant
with the installation instructions on the manual.

Also, the natural expectation is that the manual will always be up to
date, while the page might not be.

The commit promotes the rest of the page in index.org since these are
general information that can be useful to the casual reader.
.build.yml: Fix org-mode.tar.gz download path
.build.yml: Install wget
.build.yml: Upload the latest stable as org-mode.tar.gz
.build.yml: Email bzg@gnu.org about build failures
index.org: Make the git URL more prominent
Changes.org: Add new #+link shortcut to msg
Changes.org: Fake update
install.org: Advertize GNU ELPA
Changes.org: Update to 9.5 changes
Move old release notes to a new page on Worg

See https://orgmode.org/worg/org-release-notes.html