Add documentation for initial versions

[Elchi3]

This attempts to add some docs about BCD's initial versions.
Background is #6861 in which we try to fix the initial version for Node.js data.

@ddbeck sharing this early and as a draft, so we can talk about whether this is going in the direction you imagined.

For Firefox Android and the Operas I actually need to dig a bit to understand why we have these initial versions. I'm sure there are good reasons, I just need to find them :)

[ddbeck]

A very quick initial take here, but I'm very pleased by where this is headed!

One thing we're not great on is distinguishing consumer docs from contributor docs. We might be well-served by breaking this up a bit, to describe initial versions in the schema docs (alongside the ranged version info) and provide additional background and recommendations in the data guidelines.

The Node.js case is illustrative. In the schema docs, we could use the "subject to change" text you've already written. In the data guidelines we could say, "If you're adding new data, use 0.10.0 or later. If a feature was added in a version before 0.10.0, use 0.10.0 anyway."

A couple notes to help your research in the comments. When this is further along, I can revisit this for nitpicking. 😄 Thank you!

[Elchi3]

A very quick initial take here, but I'm very pleased by where this is headed!

Thanks for your very fast review! Glad I shared this early, so we can move things around.

One thing we're not great on is distinguishing consumer docs from contributor docs. We might be well-served by breaking this up a bit, to describe initial versions in the schema docs (alongside the ranged version info) and provide additional background and recommendations in the data guidelines.

Great point, forgot to look outside the docs/ folder. (silly past me who put this in the schema/ folder). I completely agree it belongs in the "consumer docs" next to ranged versions. I moved it there.

Side note: I wonder if it would be worth having "consumer docs" and "contributor docs". Maybe these would be more approachable names than "data guidelines" and "schema docs".

A couple notes to help your research in the comments.

Thanks so much! I knew these things once but forgot everything 😄

When this is further along, I can revisit this for nitpicking.

I think this is ready for you to nitpick away :)

[ddbeck]

Pretty close here. Some little suggests in line comments. Thank you, @Elchi3!

(Also, if you apply any of my suggestions, it may fail the Markdown linting. I didn't test them, sorry.)

[Elchi3]

Great suggestions, thank you Daniel! 💯

(Also, if you apply any of my suggestions, it may fail the Markdown linting. I didn't test them, sorry.)

Yeah, turns out markdown table formatting is enforced quite strictly here. (I think I prefer the compact notation, but npm run fix is helpful and gets things done anyways)

[ddbeck]

Step one complete! Thank you, @Elchi3! 🎉