[repo] Automate migration and update of page obseletion

[andrewnicols]

This commit makes use of the nodemw package
(https://github.com/macbre/nodemw) to interact with the Wikimedia API
and:

• fetch a list of all pages with the {{Template:obsolete}} template
  transcluded, updating the list of obsolete pages to warn about
• ensure that all migrated pages are correctly identified in the
  Developer Docs.

To achieve this:

• the migratedPages.js is broken out such that migrated page data is
  now read from a data/migratedPages.json file, and obsolete page data
  from a data/obsoletePages.json file.
• the migrated page JSON is modified to include both the slug, and the
  markdown path. This is to work around the difficulties of determining
  the final route on a Docusaurus page and may be fixed in future when I
  have time to work this out

This workflow is called automatically on any push to the main branch,
or on request via the Github Actions UI.

It will use a set of repository secrets for WIKIMEDIA_USER and
WIKIMEDIA_PASSWORD.

[andrewnicols]

Rebased on files changes.

[sarjona]

That's a great idea and a very good implementation, Andrew! The patch is working as expected (I've been able to execute it locally and pages for File_API and File_API_internal have been updated properly). Well done! :-)
Apart from that, I've also been able to confirm the obsoletePages.json is updated as expected.

That's a good automatisation that will help us to migrate pages. And in the near future, once the new devdocs will be ready for that, will be great to use this script to protect the migrated pages too!