Support wrapping with count (#103)

[SidOfc]

This PR adds functionality and changes some default behavior based on feature request #103.

• Instead of wrapping word, it will now wrap WORD instead (changed default behavior)
• It allows users to prefix the following mappings with a [COUNT]:
  • Wrapping bold
  • Wrapping italic
  • Wrapping strikethrough
  • Wrapping inline code
  • Wrapping links

Also added tests to verify the behavior works as intended.

Additionally, some bugs were fixed which now allow mkdx to handle wrapping single-character "words" a bit better, and wrapping last-word-in-line is also less buggy now.