[SPEC-CHANGE] Preformatted text, header and unordered list lines defined

[solderpunk]

Attention Gemininauts!

I have officially updated the spec-spec just now.
        
SUMMARY OF CHANGES:

Section 1.3.5 (text/gemini response) has been edited and expanded in
several places, to define new line types.  The only non-optional change
defines lines beginning with ``` as toggling a "preformatted" mode,
within which all lines (including those which would constitute link
lines outside of preformatted mode) must be presented verbatim in a
fixed width font.

IMPLICATIONS FOR SERVER AUTHORS:
	 
None
	  
IMPLICATIONS FOR CLIENT AUTHORS:
	   
Clients now need to detect and correctly handle preformatted lines.

Clients MAY optionally recognise heading lines and unordered list item
lines.
	    
IMPLICATIONS FOR CONTENT AUTHORS:

Authors with ASCII art, source code or other content which may appear
incorrectly when displayed in a variable width font or with minor
whitespace normalisation should enclose said content within
preformatting toggle lines.

Cheers,
Solderpunk