index StaticSearcher &'static str by &'static str

credit
- https://stackoverflow.com/questions/65549983/trait-borrowstring-is-not-implemented-for-str/65550108#65550108

tests/tests.rs

@@ -24,7 +24,7 @@ fn add_searcher_works() {
 #[test]
 fn add_static_searcher_works() {
     let lume = read_lume_to_str();
-    let name = "lume".to_string();
+    let name = "lume";
     let mut map = HashMap::new();
     map.insert(name, lume);