feat: migrate to ratatui (#26)

Co-authored-by: Ben PHL <benphawke@gmail.com>

src/flatten.rs

@@ -46,11 +46,11 @@ fn internal<'a>(
 }
 
 #[cfg(test)]
-fn get_naive_string_from_text(text: &tui::text::Text<'_>) -> String {
+fn get_naive_string_from_text(text: &ratatui::text::Text<'_>) -> String {
     text.lines
         .first()
         .unwrap()
-        .0
+        .spans
         .first()
         .unwrap()
         .content