Use correct typographic symbols in guidelines

[rettinghaus]

This PR replaces typewriter apostrophes and quotation marks with the correct typographic ones and unifies all occurrences.

[craigsapp]

The apostrophes are fixed but single-quotation endings are made worse:

(Starting quotes are being used for ending quotes).

[craigsapp]

Never mind: zooming in on them, I can now see that they are different... I searched for one, but the web browser also matches to the other.

[bwbohl]

generally I like the idea of pimping up typography in the guidelines. In some casese I wonder though, whether it would be better to come up with a stronger typed markup, e.g. for attribute values that could be markedUp using <tei:val>

[rettinghaus]

@bwbohl I like the idea using val but that should probably go with another PR. We need to add a matching rule to the css.

[kepper]

as per consensus at ODD meeting Feb 2022. Many thanks :)