Add !synopsis or similar command

[smolck]

Add command to basically post the (formatted properly) text from a given help doc, or the first x amount of it.

E.g. send !synopsis help and the bot responds with this/similar:

<Help>		or
:h[elp]			Open a window and display the help file in read-only
			mode.  If there is a help window open already, use
			that one.  Otherwise, if the current window uses the
			full width of the screen or is at least 80 characters
			wide, the help window will appear just above the
			current window.  Otherwise the new window is put at
			the very top.
			The ['helplang'](https://neovim.io/doc/user/options.html#'helplang') option is used to select a language, if
			the main help file is available in several languages.