org-keys: Bind ESC <left> by default

* lisp/org-keys.el (org-mode-map): Bind `org-metaleft' to ESC <left>
by default, not just in terminals.  This completes the ESC <arrow>
binding group.  ESC <right>, <up>, and <down> are already bound and
missing ESC <left> can be confusing.

Reported in https://orgmode.org/list/Yf6lsTR3JSNSXRDX@x.local

lisp/org-keys.el

@@ -462,6 +462,7 @@ COMMANDS is a list of alternating OLDDEF NEWDEF command names."
 
 ;;;; Cursor keys with modifiers
 (org-defkey org-mode-map (kbd "M-<left>") #'org-metaleft)
+(org-defkey org-mode-map (kbd "ESC <left>") #'org-metaleft)
 (org-defkey org-mode-map (kbd "M-<right>") #'org-metaright)
 (org-defkey org-mode-map (kbd "ESC <right>") #'org-metaright)
 (org-defkey org-mode-map (kbd "M-<up>") #'org-metaup)