Add action to deploy documentation

This was merged using Gerrit, but due to being part of the .github
directory the merge is not showing. After this commit, I will rebase 
with Gerrit.

- Action will run npm install and docs:build and push the static files
    to the gh-pages branch
- Will build documentation and push to the gh-pages branch on every
    push to master
- Tested on a forked repo: https://derick-montague.github.io/webui-vue/
- Workflow that was used is the same as being pushed with this commit:
    https://github.com/derick-montague/webui-vue/actions/runs/316032970/workflow

Author: derick-montague

.github/workflows/deploy-docs-to-gh-pages.yml

@@ -0,0 +1,34 @@
+name: Deploy documentation to GitHub pages
+on:
+  push:
+    branches: [ master ]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Generate static vuepress files
+      uses: actions/setup-node@v1
+      with:
+        node-version: '12.x'
+    - run: npm ci
+    - run: npm run docs:build
+
+    - name: Init new repo in dist folder and commit generated files
+      run: |
+        cd docs/.vuepress/dist
+        git init
+        git add -A
+        git config --local user.email "[email protected]"
+        git config --local user.name "GitHub Action"
+        git commit -m 'deploy'
+
+    - name: Force push to gh-pages branch
+      uses: ad-m/[email protected]
+      with:
+        github_token: ${{ secrets.GITHUB_TOKEN }}
+        branch: gh-pages
+        force: true
+        directory: ./docs/.vuepress/dist