Update the DITA build so we can run it from the command line and/or a GitHub action.

[billy-the-fish]

Business case - generate the api docs automatically for each release rather than have to do this by hand
Fix version -
Subject Matter Expert - Iain, max
Reviewer - Emily
Scope - You can run a dita build using the dita command line or github actions. This build should:
For each ditamap:
- Generate the api reference
- Upload it to correct directory in https://github.com/AgoraIO/API-Reference.