🧑‍💻(docker) split frontend to another file

This commit aims at improving the user experience:
- Use a dedicated `Dockerfile` for the frontend
- Run the backend and frontend in "watch"/dev mode in Docker
- Do not start all Docker instances for small tasks

README.md

@@ -33,7 +33,7 @@ The easiest way to start working on the project is to use GNU Make:
 $ make bootstrap
 ```
 
-This command builds the `app` container, installs dependencies, performs
+This command builds the `app-dev` container, installs dependencies, performs
 database migrations and compile translations. It's a good idea to use this
 command each time you are pulling code from the project repository to avoid
 dependency-related or migration-related issues.
@@ -46,6 +46,12 @@ Note that if you need to run them afterward, you can use the eponym Make rule:
 $ make run
 ```
 
+or if you want to run them in development mode (with live reloading):
+
+```bash
+$ make run-dev
+```
+
 You can check all available Make rules using:
 
 ```bash