use `function` node as a scope rather than `function_body` (#26)

queries/locals.scm

@@ -1,5 +1,5 @@
 ; Scopes
-(function_body) @local.scope
+(function) @local.scope
 
 (case_clause) @local.scope
 

test/highlight/functions.gleam

@@ -68,6 +68,13 @@ fn trial(uri) {
   }
 }
 
+fn my_uri_to_string(my_uri) -> String {
+  uri.to_string(my_uri)
+  // <- module
+  //   ^ function
+  //             ^ variable.parameter
+}
+
 fn myfun(argument) {
   let local_fun = fn(x) { x + 1 }
   //   ^ variable