Create a 0.2.x branch

[jtpio]

Similar to the 0.1.x branch: https://github.com/voila-dashboards/voila/tree/0.1.x

We should start thinking about creating a 0.2.x branch. This would make it easier to iterate on breaking changes on master (for example #846).

Non-breaking changes landing on master could then be backported to 0.2.x and 0.1.x if needed.

Ideally we would use the help of https://github.com/meeseeksmachine to do the backports easily.

[jtpio]

Looking at the current state of the repo, we should soon be able to:

• Cut a new 0.2.12 release with the recent changes. We might for a couple more PRs and fixes before doing it
• Create the 0.2.x branch
• Start merging changes for 0.3.0 like Add reveal template to core #932
• Backport master changes to 0.2.x with https://github.com/meeseeksmachine if needed

[jtpio]

0.2.12 is out: https://github.com/voila-dashboards/voila/releases/tag/0.2.12

We should be able to start targeting 0.3.0 on master and branch for 0.2.x.

[jtpio]

Closing as there is now a 0.2.x branch: https://github.com/voila-dashboards/voila/tree/0.2.x

We are planning to merge #936 next, and switch main to target 0.3.0a0 to get these changes released in pre-releases.