Chore/final design cleanup/147

[wilwade]

Problem

Mixture of small design cleanups to try to closer match the previous design.

Link to GitHub Issue(s): #147

Solution

Various small style updates for the spec.

Change summary:

• [x] Increase font size
• [x] Use Chevron
• [x] Default coal for dark mode
• [x] Fix up tables
• [x] Add bitcoin wiki to excluded link checking
• [x] Other small style fixes

Screenshots (optional):

[saraswatpuneet]

Looks 👍