fix: make more fields optional

src/model/mod_pack.rs

@@ -11,8 +11,8 @@ pub struct ModPack {
     pub name: String,
     pub author: String,
     pub version: String,
-    pub description: String,
-    pub url: String,
+    pub description: Option<String>,
+    pub url: Option<String>,
     pub mod_pack_pages: Option<Vec<ModPackPage>>,
     pub simple_mods_list: Option<Vec<SimpleMod>>,
 }