docs: add docker development environment example (#3319)

docs/04_For_Developers/07_Development_Environment_Setup.md

@@ -0,0 +1,55 @@
+These are examples of how to setup a local development environment to add bridges, improve the docs, etc.
+
+## Docker
+
+The following can serve as an example for using docker:
+
+```
+# create a new directory
+mkdir rss-bridge-contribution
+cd rss-bridge-contribution
+
+# clone the project into a subfolder
+git clone https://github.com/RSS-Bridge/rss-bridge
+```
+
+Then add a `docker-compose.yml` file:
+
+```yml
+version: '3'
+
+services:
+  rss-bridge:
+    build:
+      context: ./rss-bridge
+    ports:
+      - 3000:80
+    volumes:
+      - ./config:/config
+      - ./rss-bridge/bridges:/app/bridges
+```
+
+You can then access RSS-Bridge at `localhost:3000` and [add your bridge](../05_Bridge_API/How_to_create_a_new_bridge) to the `rss-bridge/bridges` folder.
+
+If you need to edit any other files, like from the `lib` folder add this to the `volumes` section: `./rss-bridge/lib:/app/lib`.
+
+### Docs with Docker
+
+If you want to edit the docs add this to your docker-compose.yml:
+
+```yml
+services:
+  [...]
+
+  daux:
+    image: daux/daux.io
+    ports:
+      - 8085:8085
+    working_dir: /build
+    volumes:
+      - ./rss-bridge/docs:/build/docs
+    network_mode: host
+```
+
+and run for example the `daux serve` command with `docker-compose run --rm daux daux serve`.
+After that you can access the docs at `localhost:8085` and edit the files in `rss-bridge/docs`.