[Markdown] Convert Web/API to Markdown

[wbamberg]

This is a tracking bug for actually converting Web/API to Markdown.

I think the plan could be something like:

• Get sign-off on conversion report (meaning: close [Markdown] Prepare Web/API docs for Markdowning #7898)
• Merge as many open Web/API PRs as possible
• Freeze PRs to Web/API for a little while. Ensure that all Web/API reviewers know about this!
• File a PR to convert all of Web/API to Markdown
• Ask reviewers to review converted pages
• Make any updates needed
• Merge PR (without squashing :-)
• Unfreeze PRs to Web/API

We should aim to keep the tree frozen for not more than 2 days, say. We should ensure that all reviewers know in advance when the freeze is expected to happen, and ensure all reviewers know it's actually happening.

We should have a set of volunteers to help review the PR. Suggestions:
@Rumyra
@sideshowbarker
@hamishwillee
@Elchi3
@teoli2003
@estelle
@ddbeck

Am I missing anyone?

I thought this time I could make batches of randomly selected 200 pages and each reviewer could review a batch. If we have 8 reviewers that's 1600 oages or about 1/4 the total number.

[Rumyra]

Specific Web API reviewers are: @sideshowbarker , @Elchi3 , @wbamberg , @jpmedley and myself. If everyone above is made aware along with @rachelandrew & @escattone hopefully that covers our 'Do not merge' basis 👍

[jpmedley]

When is the conversion starting?

[hamishwillee]

@jpmedley According to @wbamberg he hopes to cut a draft PR for conversion early on Monday morning, UTC time with goal being to merge Tuesday afternoon Pacific time.

[wbamberg]

I spent some time today looking at our open PRs against Web/API. I've managed to close or advance a few, and put them in a spreadsheet with my assessment of whether they might be mergeable and what would need to happen to get them merged: https://docs.google.com/spreadsheets/d/1hSffPgqB-5zPPseFY0NzJC8D3uSEF8p62vNwkGFwFLM/edit?usp=sharing . It looks to me like some of them are not going to be mergeable, some we could merge, and some are already in Markdown so no action is needed \o/.

If you are the author of one of these PRs or are involved in its review, I'd love to hear what you think. Please ask me for access if you want to edit the sheet, as I don't want to make it globally writable :).

Ping @jpmedley , @rachelandrew , @Ryuno-Ki who are authors of open PRs that need some attention or are tagged as reviewers on open PRs.

As Hamish says up there, I'd like to file a PR for conversion early Monday morning, UTC time, and freeze merges of other PRs at that point. By that time I'll have prepared bunches of randomly-selected pages for people to review, which I'll link from this issue.

[jpmedley]

Rachel and I have been submitting new content in markdown for a few weeks now. The only thing I'm really concerned about in our PRs is one's that update files still in HTML. @rachelandrew Do any of your PRs update HTML?

[escattone]

It's amazing to see this completed far earlier than I ever expected. Great work everyone! 🎉 🍾

[wbamberg]

Thanks everyone who helped get this PR merged!

In case anyone's wondering what's left, here's a spreadsheet with the remaining areas and the number of pages each one contains: https://docs.google.com/spreadsheets/d/1gIW85rRxPkgsGjYw_5wLa_kGgMeOgnfYrpWytOMD8Lw/edit?usp=sharing

Apart from marvelling at the total confusion of our top-level IA, the obvious takeaway is that these are the areas left which contain >100 pages:

Area	Page count
glossary	538
learn	362
mozilla	1135
tools	149
web/accessibility	104
web/html	234
web/svg	376