ci: add GitHub Actions workflow 'Doc'

Signed-off-by: Unai Martinez-Corral <umartinezcorral@antmicro.com>

.github/workflows/Doc.yml

@@ -0,0 +1,50 @@
+name: Docs
+
+on:
+  pull_request:
+  push:
+  schedule:
+    - cron: '0 0 * * 4'
+  workflow_dispatch:
+
+jobs:
+
+  Docs:
+    runs-on: ubuntu-latest
+    name: '📓 Docs'
+    steps:
+
+      - name: '🧰 Checkout'
+        uses: actions/checkout@v2
+        with:
+          submodules: recursive
+
+      - name: 🛠️ Setup environment
+        run: |
+          sudo apt update -qq
+          sudo apt install -y make
+          make env
+
+      - name: 📓 Build the documentation
+        run: |
+          . ./env/conda/bin/activate symbiflow-docs
+          make html
+
+      - name: '📤 Upload artifact: Sphinx HTML'
+        uses: actions/upload-artifact@v2
+        with:
+          name: Documentation-HTML
+          path: build/sphinx/html
+
+      - name: 🚀 Publish site to GitHub Pages
+        if: github.event_name != 'pull_request'
+        run: |
+          cd build/sphinx/html
+          touch .nojekyll
+          git init
+          cp ../../../.git/config ./.git/config
+          git add .
+          git config --local user.email "BuildTheDocs@GitHubActions"
+          git config --local user.name "GitHub Actions"
+          git commit -a -m "update ${{ github.sha }}"
+          git push -u origin +HEAD:gh-pages

.gitmodules

@@ -1,20 +1,20 @@
 [submodule "source/prjtrellis"]
 	path = source/prjtrellis
-	url = ../prjtrellis
+	url = https://github.com/SymbiFlow/prjtrellis
         branch = master
 [submodule "source/symbiflow-arch-defs"]
 	path = source/symbiflow-arch-defs
-	url = ../symbiflow-arch-defs
+	url = https://github.com/SymbiFlow/symbiflow-arch-defs
         branch = master
 [submodule "source/prjxray"]
 	path = source/prjxray
-	url = ../prjxray
+	url = https://github.com/SymbiFlow/prjxray
 [submodule "source/fasm"]
 	path = source/fasm
-	url = ../fasm
+	url = https://github.com/SymbiFlow/fasm
 [submodule "source/vtr-verilog-to-routing"]
 	path = source/vtr-verilog-to-routing
-	url = ../vtr-verilog-to-routing
+	url = https://github.com/SymbiFlow/vtr-verilog-to-routing
 [submodule "third_party/make-env"]
 	path = third_party/make-env
 	url = https://github.com/SymbiFlow/make-env/