Added contrib guide for browser users

doc.zih.tu-dresden.de/docs/contrib/contribute_browser.md

@@ -87,11 +87,10 @@ into the `preview` branch of the repository.
 
 * Click on "Merge requests" (in the menu to the left) as depicted below.
 * Then, click on the button "New merge request".
-* Select your source branch (for example `edits-in-document-xyz`) and click on "Compare branches and continue".
-  (The target branch is always `preview`. This is pre-selected - do not change!)
-* The next screen will give you an overview of your changes.
-* Please provide a meaningful description of the contributions.
-* Once you checked them, click on "Create merge request".
+* Select your source branch (for example `edits-in-document-xyz`) and click on "Compare branches and
+  continue". (The target branch is always `preview`. This is pre-selected - do not change!)
+* The next screen will give you an overview of your changes.  Please provide a meaningful
+* description of the contributions.  Once you checked them, click on "Create merge request".
 
 ![new merge request](misc/cb_new_merge_request.png)