Implement JSON Schema for PGXN Meta Spec v1

Based on the descriptions in `spec.md` and the validation in
pgxn/pgxn-meta-validator, write JSON Schema v2020 schemas to validate
PGXN Meta Spec `META.json` files. The implementation should be at least
as good as the old one, now portable for use in other languages.

In the process, correct a few issues and errors discovered in `spec.md`.

Add a test suite in Rust that uses the boon crate to verify that the
schemas, their IDs, and their examples are valid. This sets the stage
for writing a validation utility in Rust.

To keep things tidy and somewhat standardized, add a pre-commit
configuration to lint the JSON and Rust code.

Then setup a GitHub workflow to run the tests on macOS, Windows, and
Linux, and the pre-commit linting on Linux. Overkill for now, since
there is no Rust library, just tests for the JSON Schema, but likely to
be needed before long.

.github/workflows/test-and-lint.yml

@@ -0,0 +1,35 @@
+name: 🧪 Test and Lint
+on:
+  push:
+    branches-ignore: [wip/**]
+jobs:
+  test:
+    strategy:
+      matrix:
+        os: [[🐧, Ubuntu], [🍎, macOS], [🪟, Windows]]
+        toolchain: ["stable", "beta", "nightly"]
+    name: 🦀 ${{ matrix.toolchain }} on ${{ matrix.os[0] }} ${{ matrix.os[1] }}
+    runs-on: ${{ matrix.os[1] }}-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Rust Cache
+        uses: Swatinem/rust-cache@v2
+      - name: Setup Rust
+        uses: dtolnay/rust-toolchain@stable
+        with: { toolchain: "${{ matrix.toolchain }}" }
+      - name: Test
+        run: make test
+
+  lint:
+    name: 🔎 Lint and Cover
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Rust Cache
+        uses: Swatinem/rust-cache@v2
+      - name: Setup Rust
+        uses: dtolnay/rust-toolchain@stable
+      - name: Run pre-commit
+        uses: pre-commit/action@v3.0.1

.gitignore

@@ -1 +1,5 @@
-/.vscode
+.DS_Store
+.idea/
+/target
+.vscode/
+vendor/

.pre-commit-config.yaml

@@ -0,0 +1,29 @@
+# auth-global hooks will be managed / updated across all auth repos.
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.6.0
+    hooks:
+      - id: trailing-whitespace
+        name: Lint trailing whitespace
+        exclude_types: [image]
+      - id: end-of-file-fixer
+        name: Lint end-of-file newline
+        exclude_types: [image]
+      - id: check-added-large-files
+        name: Don't permit large files
+        exclude_types: [image]
+
+  - repo: https://github.com/backplane/pre-commit-rust-hooks
+    rev: v1.1.0
+    hooks:
+      - id: fmt
+      - id: check
+      - id: clippy
+      - id: test
+
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v3.1.0
+    hooks:
+      - id: prettier
+        name: JSON and YAML formatting
+        types_or: [json, yaml]