[3.13] gh-121746: Bind Alt+Enter to "accept" in the REPL (GH-121754) (GH-121803)

(cherry picked from commit 6522f0e)

Co-authored-by: Rodrigo Girão Serrão <5621605+rodrigogiraoserrao@users.noreply.github.com>

Author: miss-islington

Lib/_pyrepl/reader.py

@@ -130,7 +130,7 @@ def make_default_commands() -> dict[CommandName, type[Command]]:
         (r"\M-7", "digit-arg"),
         (r"\M-8", "digit-arg"),
         (r"\M-9", "digit-arg"),
-        # (r'\M-\n', 'insert-nl'),
+        (r"\M-\n", "accept"),
         ("\\\\", "self-insert"),
         (r"\x1b[200~", "enable_bracketed_paste"),
         (r"\x1b[201~", "disable_bracketed_paste"),

Misc/ACKS

@@ -1667,6 +1667,7 @@ Fred Sells
 Jiwon Seo
 Iñigo Serna
 Joakim Sernbrant
+Rodrigo Girão Serrão
 Roger D. Serwy
 Jerry Seutter
 Pete Sevander