Add four years of English from the gymnasium syllabus.

Each year mixes listening, reading, writing, gap-fill, quizzes, and a year test so the subject is usable through the maturita.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/progress.c

@@ -58,6 +58,7 @@ void load_progress(void) {
     on2_load_progress();
     on3_load_progress();
     on4_load_progress();
+    en_load_progress();
     lit_load_progress();
     sci_load_progress();
     fyz_load_progress();