feat: use docgen-action for documentation generation (#128)

Uses leanprover-community/docgen-action to build & deploy docs.

Closes #121

---------

Co-authored-by: Chris Henson <chrishenson.net@gmail.com>

Author: jessealama

.github/workflows/docs.yml

@@ -0,0 +1,33 @@
+name: Build and Deploy Documentation
+
+on:
+  push:
+    branches:
+      - main  # Build docs on merges to main
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  id-token: write
+  pages: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout project
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Build and lint the project
+        id: build-lean
+        uses: leanprover/lean-action@v1
+        with:
+          build-args: "--wfail"
+
+      - name: Build project documentation
+        id: build-docgen
+        uses: leanprover-community/docgen-action@main
+        with:
+          build-page: false

.github/workflows/lean_action_ci.yml

@@ -10,10 +10,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - if: github.event_name == 'pull_request' || (github.event_name == 'push' && github.ref == 'refs/heads/main')
-        run: |
-          set -e
-          cmp -s lean-toolchain docs/lean-toolchain
       - uses: leanprover/lean-action@v1
         with:
           build-args: "--wfail"