Skip associated types in search index

When searching for a keyword, we typically don’t want to match an
associated type.  With this patch, we skip associated types when
searching items in the search index.

src/index.rs

@@ -121,6 +121,12 @@ impl Index {
                 } else {
                     &item.path
                 };
+
+                if item.ty == 16 {
+                    // Skip associated types (== item type 16)
+                    continue;
+                }
+                
                 let full_path = match item.parent {
                     Some(idx) => {
                         let parent = &data.paths[idx].1;