Support for Experience Builder

Goals

There's no detailed plan at the moment. The repository for this issue holds some code; when and how this will find its way to the main module is unknown.

Status

A tree of XB components (as edited in the XB UI) can produce... some kind of (JSON) output.

See details and installation instructions in modules/custom_elements_xb/README.md.

Next steps

• test more complicated Single Directory Components (only simple ones have been seen to work so far)
• support for blocks
• talk to front end people and see how the output should change, to be useful