[mlpack] mlpack accepted to Google Summer of Code 2022!

[Marcus Edel]

Hello everyone,

Today Google announced that mlpack has been accepted as a mentoring organization
to Google Summer of Code 2022. Thanks to everyone who made this possible. This
will be our ninth year participating in the program.

Typically this means that there will be a lot of mailing list, chat channel, and
Github activity in the leadup to GSoC and during the summer. Each year there are
always lots of contributions both in the spring months and during the summer,
and lots of new contributors. So, a warm welcome to anyone who comes to our
community via GSoC.

If you're new to the community, keep in mind that writing code isn't the only
way to help out! It's just as helpful to answer others' questions and review
other PRs as to contribute code.

I am already excited about this year; so once again welcome to anyone who
joins our community.

Thanks
Marcus