fix(cli): add type annotation

It seems to be required when building with an older rustc version.
This did work in nightly, and just seems to be some sort of limiation
in stable.

src/mako/cli/lib/engine.mako

@@ -387,7 +387,9 @@ for kvarg in ${opt_values(KEY_VALUE_ARG)} {
         continue;
     }
    
-    let type_info = 
+    ## This type-annotation is not required in nightly (or newer rustc)
+    ## TODO(ST): try to remove it once there is a newer stable
+    let type_info: Option<(&'static str, JsonTypeInfo)> = 
         match &temp_cursor.to_string()[..] {
     % for schema, fe, f in schema_fields:
 <%