Documentation translation (#199)

Documentation translation using weblate.

* Use po4a to generate .po files from the english markdowns, then to generate translated files
* Some pages can be marked as «english only» (for technical documentation for example)
* New Hugo shortcode to use application strings in documentation (for example for settings names)
* The code of conduct is no more translated, but there is a link to official Contributor Covenant translations
* Adding all plugin's supported languages

Related to https://github.com/JohnXLivingston/peertube-plugin-livechat/issues/117

.github/workflows/gh-pages.yml

@@ -8,19 +8,25 @@ on:
 
 jobs:
   deploy:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - uses: actions/checkout@v3
         with:
           submodules: true  # Fetch Hugo themes (true OR recursive)
           fetch-depth: 0    # Fetch all history for .GitInfo and .Lastmod
 
+      - name: Install po4a
+        run: sudo apt update && sudo apt install po4a -y
+
       - name: Setup Hugo
         uses: peaceiris/actions-hugo@v2
         with:
           hugo-version: '0.80.0'
           # extended: true
 
+      - name: Generate documentation translations
+        run: bash ./doc-translate.sh
+
       - name: Build
         run: hugo --minify --baseURL='https://johnxlivingston.github.io/peertube-plugin-livechat' -s support/documentation