add parallel tut to nav + index

Author: SamGuay

docs/tutorial/index.md

@@ -9,6 +9,8 @@ commands.
 
 [First steps with dcm2bids](first-steps.md){ .md-button .md-button--primary }
 
+[Convert multiple participants in parallel](parallel.md){ .md-button .md-button--primary }
+
 ---
 
 !!! tldr "Interested in co-developing a tutorial?"

mkdocs.yml

@@ -22,6 +22,7 @@ nav:
   - Tutorials:
       - index: tutorial/index.md
       - First steps: tutorial/first-steps.md
+      - Multiple participants in parallel: tutorial/parallel.md
   - How-to guides:
       - index: how-to/index.md
       - Get help and support: how-to/get-help.md