Add some personal obsidian configs

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/user/configs/gui/obsidian/options.nix

@@ -123,6 +123,7 @@ in
             extraFiles = mkOption {
               type = attrsOf (submodule pluginsExtraFilesOptions);
               description = "Additional files to include in the plugin directory.";
+              default = { };
             };
           };
         };