docs: Set Obsidian preferences to 2-space indentation

This is for consistency with the lint:markdown behaviour.

Author: claremacrae

docs/.obsidian/app.json

@@ -10,5 +10,6 @@
   "promptDelete": false,
   "showInlineTitle": false,
   "alwaysUpdateLinks": true,
-  "useMarkdownLinks": false
+  "useMarkdownLinks": false,
+  "tabSize": 2
 }