[SPECS text/gemini] Heading lines proposal

[solderpunk]

On Sun, Jun 14, 2020 at 11:07:31AM +0200, cage wrote:

> For example if i starts a line mentioning an IRC channel like that:
> 
> #channel [...]
> 
> this would be presented  to the user as an header of  level 1 which is
> not.
> 
> The same would be true if i mention a tag for a social network.

I guess this is just as good an argument as the *emphasised* words
clashing with list items thing.  AFAIK it hasn't been spotted in the
wild yet, but that's probably just a function of Geminispace being young
and small.

> As for the  list item i think would  be a good idea to add  a space to
> the header mark: so from "#" to  "#<space>" and so on for header level
> 2 and 3.

This would be covered by Petite Abeille's proposal to just put a
mandatory space after *all* the special line indicators.

Is it silly that I'm sad this would require (on account of
### sub-sub-headings) changing "It is possible to unambiguously
determine a line's type purely by inspecting its first three characters"
to "first four characters"?  It is silly.  But three just feels like a
much more *natural* choice of entirely arbitrary small number...

Cheers,
Solderpunk