Update sidebar

Author: biboudis

docs/sidebar.yml

@@ -17,14 +17,16 @@ sidebar:
       subsection:
         - title: Getting Started
           url: docs/contributing/getting-started.html
-        - title: IntelliJ IDEA
-          url: docs/contributing/intellij-idea.html
-        - title: Eclipse
-          url: docs/contributing/eclipse.html
         - title: Workflow
           url: docs/contributing/workflow.html
+        - title: Eclipse
+          url: docs/contributing/eclipse.html
+        - title: IntelliJ IDEA
+          url: docs/contributing/intellij-idea.html
         - title: Testing
           url: docs/contributing/testing.html
+        - title: Working with the Backend
+          url: docs/contributing/backend.md
     - title: Internals
       subsection:
         - title: Backend