[REQ] Document how explicit spaces should be represented in verbatim formatting

[mhatzl]

Inline formatting are only valid if open keyword is followed by non-whitespace and closing preceded by non-whitespace.
This makes it impossible to have whitespace at start or end of verbatim formatting.

However, whitespace at start and end would be hard to read anyways.
A better alternativ is to use certain Unicode symbols to explicitly show that a whitespace is required here.
Some good symbols are mentioned in this stackexchange post.

In short:

• For keyboard-space
  • Good font coverage: U+2423 Open Box "␣"
  • Looks better: U+23B5 Bottom Square Bracket "⎵"
• For spaces between words
  • Good font coverage: U+00B7 Middle dot "·"
  • Looks better: U+2E31 Word Separator Middle Dot "⸱"

This should be documented in the verbatim formatting section.