Add Easy Template for COMMENT (C)

* lisp/org.el: (org-structure-template-alist): Added `COMMENT' block template
  bound to `C'

* doc/org.texi: Add documentation for `COMMENT' Easy Template.

* contrib/orgmanual.org: Add documentation for `COMMENT' Easy
  Template.

* etc/ORG-NEWS: Added note for 9.1 release under Miscellaneous

contrib/orgmanual.org

@@ -15922,6 +15922,7 @@ The following template selectors are currently supported:
 | {{{kbd(a)}}} | ~#+BEGIN_ASCII~ ...~ #+END_ASCII~     |
 | {{{kbd(A)}}} | ~#+ASCII:~                            |
 | {{{kbd(c)}}} | ~#+BEGIN_CENTER~ ... ~#+END_CENTER~   |
+| {{{kbd(C)}}} | ~#+BEGIN_COMMENT~ ... ~#+END_COMMENT~ |
 | {{{kbd(e)}}} | ~#+BEGIN_EXAMPLE~ ... ~#+END_EXAMPLE~ |
 | {{{kbd(h)}}} | ~#+BEGIN_HTML~ ... ~#+END_HTML~       |
 | {{{kbd(H)}}} | ~#+HTML:~                             |

doc/org.texi

@@ -17347,6 +17347,7 @@ Org comes with these pre-defined easy templates:
 @item @kbd{q} @tab @code{#+BEGIN_QUOTE ... #+END_QUOTE}
 @item @kbd{v} @tab @code{#+BEGIN_VERSE ... #+END_VERSE}
 @item @kbd{c} @tab @code{#+BEGIN_CENTER ... #+END_CENTER}
+@item @kbd{C} @tab @code{#+BEGIN_COMMENT ... #+END_COMMENT}
 @item @kbd{l} @tab @code{#+BEGIN_EXPORT latex ... #+END_EXPORT}
 @item @kbd{L} @tab @code{#+LATEX:}
 @item @kbd{h} @tab @code{#+BEGIN_EXPORT html ... #+END_EXPORT}

etc/ORG-NEWS

@@ -466,6 +466,8 @@ suitable as a default value.
     URLs like =https://cool-blog.com/2017/05/20/cool-post/= are
     covered by rewrite rules.
 
+*** Add (C) =COMMENT= support to ~org-structure-template-alist~
+
 * Version 9.0
 
 ** Incompatible changes

lisp/org.el

@@ -12179,6 +12179,7 @@ keywords relative to each registered export back-end."
     ("v" "#+BEGIN_VERSE\n?\n#+END_VERSE")
     ("V" "#+BEGIN_VERBATIM\n?\n#+END_VERBATIM")
     ("c" "#+BEGIN_CENTER\n?\n#+END_CENTER")
+    ("C" "#+BEGIN_COMMENT\n?\n#+END_COMMENT")
     ("l" "#+BEGIN_EXPORT latex\n?\n#+END_EXPORT")
     ("L" "#+LaTeX: ")
     ("h" "#+BEGIN_EXPORT html\n?\n#+END_EXPORT")