Update docs

[lochhh]

This PR updates the aeon_docs website by:

• updating submodules to the latest commits
• populating the aeon docs website with contents from:
  • aeon_docs/readme.md
  • aeon_blog/data_contract.md
  • aeon_blog/design_considerations.md
  • aeon_blog/code_of_conduct.md
  • aeon_blog/style_and_doc_guidelines.md
• automatically generating aeon_mecha API docs (ignoring aeon.dj_pipeline and aeon.qc.video modules) when building docs
• removing tracking of built docs (hence the large number of changed files)

This PR also

• adds instructions on building the documentation in aeon_docs/readme.md
• adds a GitHub actions workflow to build and deploy docs to the gh-pages branch

The built docs of the forked repository is live here.

[jkbhagatio]

Once the build dir (docs/) is ignored, happy to merge!