Update CONTRIBUTING.md

fix markdown rendering

Author: hotzenklotz

CONTRIBUTING.md

@@ -114,6 +114,7 @@ See below for specifics of the different packages. Let's have a look at the comm
   [`pip install -f requirements.txt`](https://github.com/scalableminds/webknossos-libs/blob/master/requirements.txt)
 
   To install the dependencies for all sub-projects, run `make install`.
+  
 * **Tooling** we use across the sub-projects to enforce coding styles and tests:
     * `./format.sh`: black and isort
     * `./lint.sh`: pylint