[DOC] upgrade_analysis : update roadmap.rst + add maintainers

[legalsylvain]

Add new item in the roadmap section for the next migration of the module in V16

See : OCA/OpenUpgrade#3209 (comment)

CC : @StefanRijnhart

[legalsylvain]

thanks for your review.

fastracking trivial patch

/ocabot merge patch

[OCA-git-bot]

Sorry @legalsylvain you are not allowed to merge.

To do so you must either have push permissions on the repository, or be a declared maintainer of all modified addons.

If you wish to adopt an addon and become it's maintainer, open a pull request to add your GitHub login to the maintainers key of its manifest.

[legalsylvain]

FYI, I added me as maintainers to avoid such situation. hope is ok for you.
@StefanRijnhart : let me know if you want to be set as maintainer as well.

[StefanRijnhart]

Can you add me as a maintainer as well?

[legalsylvain]

Can you add me as a maintainer as well?

Of course. done.

[StefanRijnhart]

Thanks!

/ocabot merge patch

[OCA-git-bot]

This PR looks fantastic, let's merge it!
Prepared branch 15.0-ocabot-merge-pr-2361-by-StefanRijnhart-bump-patch, awaiting test results.

[OCA-git-bot]

Congratulations, your PR was merged at 9c059f4. Thanks a lot for contributing to OCA. ❤️