contrib: Install and enable the "Vault Nickname" plugin

So that in Obsidian I can distinguish between identically-named
vaults from the maine Tasks repo and my fork.

Author: claremacrae

contributing/.obsidian/community-plugins.json

@@ -8,5 +8,6 @@
   "templater-obsidian",
   "tag-wrangler",
   "broken-links",
-  "obsidian-plugin-update-tracker"
+  "obsidian-plugin-update-tracker",
+  "vault-nickname"
 ]