chore(git): exclude plans directory from version control

- Add plans/ to .gitignore
- Remove previously tracked plans/ files from git index
- Plan files remain on disk but are no longer committed

Author: gevik

.gitignore

@@ -27,3 +27,6 @@ yarn-error.log*
 
 # Package tarballs
 *.tgz
+
+# Plans
+plans/