org-entities.el: Add parallel symbol

* org-entities.el (org-entities): Add parallel symbol.

From patch proposal by Brady Trainor.

TINYCHANGE

lisp/org-entities.el

@@ -394,6 +394,7 @@ packages to be loaded, add these packages to `org-latex-packages-alist'."
     ("ang" "\\angle" t "∠" "[angle]" "[angle]" "∠")
     ("angle" "\\angle" t "∠" "[angle]" "[angle]" "∠")
     ("perp" "\\perp" t "⊥" "[up tack]" "[up tack]" "⊥")
+    ("parallel" "\\parallel" t "∥" "||" "||" "∥")
     ("sdot" "\\cdot" t "⋅" "[dot]" "[dot]" "⋅")
     ("cdot" "\\cdot" t "⋅" "[dot]" "[dot]" "⋅")
     ("lceil" "\\lceil" t "⌈" "[left ceiling]" "[left ceiling]" "⌈")