Fix date format (#71)

src/search/indexing/curseforge_import.rs

@@ -197,9 +197,9 @@ pub async fn index_curseforge(
             page_url: curseforge_mod.website_url,
             icon_url,
             author_url: (&curseforge_mod.authors[0].url).to_string(),
-            date_created: created.to_string(),
+            date_created: created.to_rfc3339(),
             created_timestamp: created.timestamp(),
-            date_modified: modified.to_string(),
+            date_modified: modified.to_rfc3339(),
             modified_timestamp: modified.timestamp(),
             latest_version,
             host: Cow::Borrowed("curseforge"),