Migrate from MdBook to MkDocs (#5062)

## Summary

We want to have consistency between the Ruff and uv documentation for
the upcoming release. We don't love the Ruff docs, but we'd rather have
consistency and then work towards improving them both, rather than have
two very-different documentation sites that both have weaknesses.

The setup here is simpler than in Ruff as: (1) we don't yet generate any
docs from Rust and (2) we don't try to reuse the README in the uv
documentation (which adds a lot of complexity in Ruff). So the change
here is mostly a 1-to-1 port to MkDocs.

## Test Plan

![Screenshot 2024-07-14 at 9 49
15 PM](https://github.com/user-attachments/assets/8bfb5b06-08ff-4329-b368-d9087b78996e)

.github/workflows/docs.yml

@@ -1,49 +0,0 @@
-name: Publish documentation
-
-on:
-  push:
-    branches: ["main"]
-
-  # Allows you to run this workflow manually from the Actions tab
-  workflow_dispatch:
-
-# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
-permissions:
-  contents: read
-  pages: write
-  id-token: write
-
-# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
-# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
-concurrency:
-  group: "docs"
-  cancel-in-progress: false
-
-jobs:
-  deploy:
-    environment:
-      name: github-pages
-      url: ${{ steps.deployment.outputs.page_url }}
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-      - name: Install latest mdbook
-        run: |
-          tag=$(curl 'https://api.github.com/repos/rust-lang/mdbook/releases/latest' | jq -r '.tag_name')
-          url="https://github.com/rust-lang/mdbook/releases/download/${tag}/mdbook-${tag}-x86_64-unknown-linux-gnu.tar.gz"
-          mkdir mdbook
-          curl -sSL $url | tar -xz --directory=./mdbook
-          echo `pwd`/mdbook >> $GITHUB_PATH
-      - name: Build mdbook
-        run: |
-          mdbook build docs
-      - name: Setup Pages
-        uses: actions/configure-pages@v5
-      - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
-        with:
-          path: "docs/book"
-      - name: Deploy to GitHub Pages
-        id: deployment
-        uses: actions/deploy-pages@v4

.github/workflows/publish-docs.yml

@@ -0,0 +1,50 @@
+# Publish the uv documentation.
+#
+# Assumed to run as a subworkflow of .github/workflows/release.yml; specifically, as a post-announce
+# job within `cargo-dist`.
+name: mkdocs
+
+on:
+  workflow_dispatch:
+    inputs:
+      ref:
+        description: "The commit SHA, tag, or branch to publish. Uses the default branch if not specified."
+        default: ""
+        type: string
+
+jobs:
+  mkdocs:
+    runs-on: ubuntu-latest
+    env:
+      CF_API_TOKEN_EXISTS: ${{ secrets.CF_API_TOKEN != '' }}
+      MKDOCS_INSIDERS_SSH_KEY_EXISTS: ${{ secrets.MKDOCS_INSIDERS_SSH_KEY != '' }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+      - uses: actions/setup-python@v5
+      - name: "Add SSH key"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        uses: webfactory/ssh-agent@v0.9.0
+        with:
+          ssh-private-key: ${{ secrets.MKDOCS_INSIDERS_SSH_KEY }}
+      - name: "Install Insiders dependencies"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        run: pip install -r docs/requirements-insiders.txt
+      - name: "Install dependencies"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS != 'true' }}
+        run: pip install -r docs/requirements.txt
+      - name: "Build Insiders docs"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS == 'true' }}
+        run: mkdocs build --strict -f mkdocs.insiders.yml
+      - name: "Build docs"
+        if: ${{ env.MKDOCS_INSIDERS_SSH_KEY_EXISTS != 'true' }}
+        run: mkdocs build --strict -f mkdocs.public.yml
+      - name: "Deploy to Cloudflare Pages"
+        if: ${{ env.CF_API_TOKEN_EXISTS == 'true' }}
+        uses: cloudflare/wrangler-action@v3.7.0
+        with:
+          apiToken: ${{ secrets.CF_API_TOKEN }}
+          accountId: ${{ secrets.CF_ACCOUNT_ID }}
+          # `github.head_ref` is only set during pull requests and for manual runs or tags we use `main` to deploy to production
+          command: pages deploy site --project-name=uv-docs --branch ${{ github.head_ref || 'main' }} --commit-hash ${GITHUB_SHA}