The master branch is now closed for new libraries and breaking
changes, and will be closing for the beta in one week. 

Also, if you're ready, you can also add your libraries' changes to the
release notes at:

<https://github.com/boostorg/website/blob/master/feed/history/boost_1_69_0.qbk>

After editing the release notes, you should get a form to create a
pull request, remember to submit it, otherwise I won't see your
change.

Thanks,

-- The Boost Release Team