new internal structure for proposals

Author: rkweehinzmann

.github/mkdocs/mkdocs.yaml

@@ -14,7 +14,8 @@ nav:
       - datasets/index.md
       - Publishing data: datasets/Publishing.md
       - Publishing data Advanced: datasets/PublishingAdvanced.md
-    - Proposals: proposals.md
+    - Proposals: 
+      - proposals/index.md
     - Samples: samples.md
     - Instruments: instruments.md
     - Troubleshooting: