A proposed scheme for parsing preformatted alt text

[Luke Emmet]

Hi All

We had an interesting discussion on the #Gemini IRC channel earlier 
today about a generalised scheme for parsing the alt text on 
preformatted regions, e.g.

```this is the alt text, not normally displayed to the end user
the preformatted content
```

It was a collective discussion, but I've written up some of the key 
points in a post here:

gemini://gemini.marmaladefoo.com/blog/7-Sep-2020_Parsing_preformatted_alt_text.gmi

Essentially the key design considerations are as follows:

1. By default the whole alt text can be used as a label (current behaviour)
2. Use CSS style syntax for the remainder, a familiar and low ritual syntax
3. Don't prescribe the attributes, allow practice to suggest them
4. Be backwards compatible and friendly to screen readers etc.

two initial attributes seem to have obvious initial utility and could be 
used to effectively label content in a practical way:

content-type
lang

Best Wishes

  - Luke