Add translations doc

README.md

@@ -11,3 +11,29 @@ $ npm run serve
 ```
 $ npm run build
 ```
+
+## Update translations
+
+Add Weblate remote:
+
+```
+$ git remote add weblate https://weblate.framasoft.org/git/joinpeertube/main
+```
+
+Update from Weblate:
+
+```
+$ git fetch weblate && git merge weblate/master
+```
+
+Re generate translations:
+
+```
+$ npm run i18n:generate
+```
+
+Push on master (Weblate will be automatically updated)
+
+```
+$ git push origin master
+```