Wrap text for code rendering

[AlexHuang2]

Noticed that code renderings do not wrap text and when exported to PDF, cuts off.

[kg4zow]

Some people may not want code blocks to wrap, or at least, not every time a document is printed.

I think there should be an option on each print job to allow the user to control whether it wraps or not, with a preference to set the default value of this option.

[schuyler]

This issue has been addressed in MacDown 3000.

The fix implements @media print CSS that forces code blocks to wrap in PDF exports:

• white-space: pre-wrap for <pre> and <code> elements
• overflow-wrap: break-word to prevent overflow
• Special handling for tables containing code

Based on the approach from PR #1349 by @falkorichter.