feat: generate frictionless data package metadata (vega#631)

* feat: generate `frictionless` data package metadata

Closes vega#629

- Adds `build_datapackage.py` script
- Generates initial metadata in both `.yaml` and `.json` formats

* feat(typing): spell mappings more explicitly

Improves readability, but mainly to support per-resource `description`, `sources`, `licenses`
See vega#631 (comment)

* refactor(ruff): misc linting

* ci: change default output to `json`, fix missing `contributors`

vega#631 (review), vega#631 (comment)

* feat: add support for `.arrow`

vega#631 (comment), vega#631 (comment)

* feat(DRAFT): add `.with_extras()`, for `description`, `source`, and `license`

Unused currently, depends on having a more structured `SOURCES.md`

vega#631 (comment)

* add data package to build step

* ci: add uv

* ci: fix uv setup

* ci: fail if there are changes

* just kidding (timestamps change things)

* chore: update pr template

---------

Co-authored-by: Dominik Moritz <[email protected]>

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,3 +1,4 @@
 Please:
 - [ ] Update the changelog in `README.md`. Add a new version if needed and add a short description of the change.
 - [ ] Add information about new datasets to `sources.md`.
+- [ ] Only add the `datapackage.json` if there are changes to it besides the timestamp.

.github/workflows/test.yml

@@ -23,6 +23,10 @@ jobs:
           cache: 'npm'
           node-version: 20
 
+      - uses: astral-sh/setup-uv@v3
+        with:
+          version: ">=0.5.0"
+
       - name: Install Node dependencies
         run: npm ci