Customise the first post in o2 for Rosetta o2s

[pento]

Here's some text from @samuelsidler.

Welcome to Your Team's O2!

We're happy to give each translation team their own blog, allowing you to coordinate easier, right on WordPress.org. You can customize this site and add pages, as needed. If you have questions, <a href="https://make.wordpress.org/meta/">let the meta team know</a>.

<h2>How to use O2</h2>

O2 is a combination of a theme and a plugin that allows for easier collaboration. Here are a few features that will be helpful to coordinating your team's activities:

# @mentions: Mention anyone on the WordPress.org network by putting an @ in front of their username. Members of your locale sites (including your main site, your forums, and O2) are automatically added to autocomplete.
# Tags: Tagging can be added easily with the # tag and can now be added inline in posts. Click on a tag and to see all tagged posts.
# Cross posts: Cross post to another O2 site on WordPress.org by using the + symbol. You can cross post to any site that's using O2.

<hr />

That's it! Enjoy your new blog and <a href="https://meta.trac.wordpress.org/newticket?component=Make+(Get+Involved)+%2F+P2">file meta tickets</a> if you run into any issues.

[samuelsidler]

Updated the tagging section a little bit.

[samuelsidler]

Fixed in [12171-dotorg].