WIP: Subproject ngff-spec under specfications directory

[jo-mueller]

Fixes #399

This is a proposed solution on how a joint layout of the ngff page and the future home of the spec, ome/ngff-spec could look like.

Key changes:

• Deprecated bikeshed: The specs of .5 and 0.6.dev2 were converted into markdown and are added as submodules under the specifications folder here in ngff
• Moved submodules: As mentioned before, I removed the current submodule structure with the versions on the repo root and the spec versions living on different branches of this repo. Instead, the submodules point to different branches of the ngff-spec repo
• Consistent build: Since the spec is now written in markdown, the respective md-pages can simply be added to a sphinx toctree directive over here on the ngff page - and as such be part of a uniform page layout.

What I'll try to get working, is that the additional contents of the ngff-spec pages as RTD builds them right now are not yet part of the joint web layout this PR brings. In particular, this includes:

• rendered schemas
• rendered examples
• changelog, version history, which are separate md pages over at ngff-spec

Still, I figure this is a good starting point to improve the overall appearance of the ngff page, make it easier to access and contribute to the spec and address a bunch of issues (see #399)

[github-actions]

Automated Review URLs

• Readthedocs
• render latest/index.bs
• diff latest modified

[lubianat]

should we move with

• change layout and add navbar #408
  before this one?

preview on your link looks good, though

[jo-mueller]

@lubianat #408 makes total sense to go in first. On second and third thought, I think I may also undo the RTD deprecation in here. My original reason for doing this in the first place was the lack of customization options on how to integrate ngff-spec pages in the ngff page.

But since the placing of the spec submodules under the /specifications directory and the direct inclusion into the ngff page's toctree kind of solve that, maybe that's not an urgent need.

[lubianat]

I know this is WIP, but I don't really see 0.1, 0.2 etc there. Am I doing something wrong?

[jo-mueller]

@lubianat not at all :) We only merged the backport for 0.1...0.4 last week and I haven't updated the submodule configuration here yet. Will do asap!

[jo-mueller]

Oh wait, they're already added, then something else is wrong 🤔