add back newlines

Author: saviorand

lightbug_http/header.mojo

@@ -115,4 +115,4 @@ struct Headers(Writable, Stringable):
             write_header(writer, header[].key, header[].value)
 
     fn __str__(self) -> String:
-        return String.write(self)
+        return String.write(self)

lightbug_http/strings.mojo

@@ -64,4 +64,4 @@ fn find_all(s: String, sub_str: String) -> List[Int]:
     while current_idx > -1:
         match_idxs.append(current_idx)
         current_idx = s.find(sub_str, start=current_idx + 1)
-    return match_idxs^
+    return match_idxs^