Start 1.1.0 from 1.0.0 with simplified branch setup

[ralfhandl]

As discussed in today's Overlays Meeting #172, use a simplified approach where everything happens on main with short-lived PR branches (preferrably in forks).

On release a spec version is moved from dev-versions to versions, preserving its commit history. Its schema and schema test folders are renamed and lose the -dev suffix.

Schema versions are in perpetual maintenance and start directly in the schemas folder.

Commit c4a5c3e adds file dev-versions/1.1.0.md which is an adjusted copy of versions/1.0.0.md:

$ diff ./dev-versions/1.1.0.md versions/1.0.0.md 
7c7
< ## Version 1.1.0
---
> ## Version 1.0.0
284d283
< | 1.1.0 | TBD | Release of the Overlay Specification 1.1.0 |

Commit 1328218 adds folder schemas/v1.1-dev which is an adjusted copy of schemas/v1.0:

diff schemas/v1.1-dev/schema.yaml schemas/v1.0/schema.yaml
1c1
< $id: https://spec.openapis.org/overlay/1.1/schema/WORK-IN-PROGRESS
---
> $id: https://spec.openapis.org/overlay/1.0/schema/WORK-IN-PROGRESS
3c3
< description: The description of Overlay v1.1.x documents
---
> description: The description of Overlay v1.0.x documents
8c8
<     pattern: ^1\.1\.\d+$
---
>     pattern: ^1\.0\.\d+$

and similar adjustments in file README.md.

It also adds folder tests/v1.1-dev which is an adjusted copy of tests/v1.0, the only difference being the value of the overlay field in the pass and fail test cases, for example

diff tests/v1.0/fail/actions-invalid-description.yaml tests/v1.1-dev/fail/actions-invalid-description.yaml
1c1
< overlay: 1.0.0
---
> overlay: 1.1.0

It also adjusts related scripts and workflows:

• .github/workflows/schema-publish.yaml has an adjusted branch name and an updated list of reviewers
• scripts/schema-publish.sh skips folders for schemas under development with suffix -dev
• tests/schema.test.mjs moved to the parent folder and now loops over all schema version folders

Commit d29c651 updates section "Branching Strategy" in CONTRIBUTING.md and describes the new setup.

[ralfhandl]

I think I covered everything now in the added CONTRIBUTING.md

[mikekistler]

Looks good! 👍