Add a GH workflow for the generation and deployment of documentation.

Author: surlymoor

.github/workflows/docs.yml

@@ -0,0 +1,39 @@
+# Builds the documentation, with the latest adrdox, with every push to master,
+# and deploys it to the gh-pages branch. Derived from Paul Backus'
+# https://github.com/pbackus/sumtype/blob/master/.github/workflows/docs.yml.
+
+name: Documentation
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  docs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+        with:
+          persist-credentials: false
+
+      - name: Install D compiler
+        uses: dlang-community/setup-dlang@v1
+        with:
+          compiler: dmd-latest
+
+      - name: Build documentation
+        run: |
+          wget https://github.com/adamdruppe/adrdox/archive/master.zip
+          unzip master.zip
+          pushd adrdox-master && make && popd
+          export PATH=$PATH:$PWD/adrdox-master
+          doc2 --genSearchIndex --genSource -o generated-docs source
+
+      - name: Deploy to Github Pages
+        uses: JamesIves/github-pages-deploy-action@3.7.1
+        with:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          BRANCH: gh-pages
+          FOLDER: generated-docs