docs: infrastructure.md: document Pages configuration for docs.yml workflow

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>

Author: threexc

docs/infrastructure.md

@@ -66,3 +66,25 @@ regenerated by a project administrator/owner.
 |-------|-------|------|--------|----------|--------|
 | `PYTHON_CI_GROUP_TOKEN` | Group ([Python](https://gitlab.com/riseproject/python)) | Maintainer | `api`, `read_api`, `read_repository`, `write_repository` | MR pipeline triggers, auto updates/checks | 1 year (April 19th, 2027) |
 | `rise-github-package-registry` | Repository deploy token ([wheel_builder](https://gitlab.com/riseproject/python/wheel_builder/-/settings/repository#js-deploy-tokens)) | n/a (deploy token) | `read_package_registry`, `write_package_registry` | Push wheels GitHub → GitLab package registry | 1 year (June 29th, 2027) |
+
+## GitHub Pages Configuration
+
+The `.github/workflows/docs.yml` workflow handles building and deploying
+documentation, including providing previews of the docs on a per-PR basis. For
+this to work correctly, the following settings need to be configured under
+`Settings -> Pages -> Build and deployment` in the repository:
+
+1. `Source` should be set to `Deploy from a branch`
+2. `Branch` should be set to `gh-pages` `/(root)`
+
+When this is configured, any changes touching the `docs` folder will trigger a
+docs build, where upon completion the `rossjrw/pr-preview-action` will
+automatically comment on the PR with a link looking like:
+
+```
+https://riseproject-dev.github.io/python-wheels/pr-preview/pr-171/
+```
+
+Note that the `gh-pages` branch should be automatically created by the
+workflows, but if not it must be created manually with an empty `.nojekyll` file
+in the project root to avoid long rebuild times.