Use New installation methods for CKEditor5

I have a proof of concept from last year that successfully does this, and the CK team + several committers were in support of the approach. The biggest part will likely be finalizing ✨ Add an API for importmaps Active , after which most of the CK changes are not too intense.

I also created a doc that details the approach and provides steps for several contrib modules on how to approach it

Have we already decided to use import map? Another option with the new installation method is using UMD build, which shouldn't be blocked by anything

ESM + import map approach gives contrib maintainers the ability to support both types of CKEditor5 builds with a single codebase.

I don't believe the UMD approach can accommodate that, which would mean maintainers having to maintain two separate versions, one that uses imports and the other pulling from the global CKEditor. If there's a way around that - great. If not, then I suppose we need to decide what tradeoffs are acceptable.