[O] [Feature Request] Add an dispatcher command (keybinding) for inserting dynamic blocks

[stardiviner]

In package `orgtbl-aggregate` has bellowing command to insert different dynamic 
blocks.

#+begin_src emacs-lisp
(defun org-insert-dblock ()
  "Inserts an org table dynamic block.
This is a dispatching function which prompts for the type
of dynamic block to insert. It dispatches to functions
which names matches the pattern `org-insert-dblock:*'"
  (interactive)
  (let ((fun
         (intern
          (format
           "org-insert-dblock:%s" 
           (org-icompleting-read
            "Kind of dynamic block: "
            (mapcar (lambda (x)
                      (replace-regexp-in-string
                       "^org-insert-dblock:"
                       ""
                       (symbol-name x)))
                    (apropos-internal "^org-insert-dblock:")))))))
    (if (functionp fun)
        (funcall fun)
      (message "No such dynamic block: %s" fun))))
#+end_src

This command matches Org Mode API style.

I hope Org Mode can have this built-in. Because there are some other dynamic 
blocks. They can use this dispatcher function.

For example org-gantt dynamic block, I write a function manually:

#+begin_src emacs-lisp
(defun org-insert-dblock:org-gantt ()
  "Insert org-gantt dynamic block."
  (interactive)
  (org-create-dblock
   (list :name "org-gantt"
         :file "data/images/project-gantt-chart.png"
         :imagemagick t
         :tikz-options "scale=1.5, every node/.style={scale=1.5}"
         :weekend-style "{draw=blue!10, line width=1pt}"
         :workday-style "{draw=blue!5, line width=.75pt}"
         :show-progress 'if-value
         :progress-source 'cookie-clocksum
         :no-date-headlines 'inactive
         :parameters "y unit title=.7cm, y unit chart=.9cm"
         :tags-group-style '(("test"."group label font=\\color{blue}")
                             ("toast"."group label font=\\color{green}"))
         :tags-bar-style '(("test"."bar label font=\\color{blue}")
                           ("toast"."bar label font=\\color{green}")))))
#+end_src

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[ stardiviner ]
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