Add ability to get playback-time

test/mpv/control_test.gleam

@@ -2,6 +2,7 @@ import gleam/list
 import gleeunit
 
 import mpv/control.{type Control}
+import mpv/internal/control as control_internal
 import mpv/key.{type Key, Char}
 
 pub fn main() -> Nil {
@@ -22,3 +23,11 @@ pub fn control_from_key_test() {
     assert tc.expected == control.from_key(tc.key)
   })
 }
+
+pub fn parse_playback_time_test() {
+  let json_string =
+    "{\"data\":\"123.456789\",\"request_id\":0,\"error\":\"success\"}\n"
+
+  let assert Ok(data) = control_internal.parse_playback_time(json_string)
+  assert data == 123.456789
+}