Check all external links

[bparks13]

Since this is describing a specification, it should for the most part be completely self-contained. Verify that there are minimal links externally that need to be maintained long-term.

[jonnew]

Most of the external links occur in the API section and will be removed with #67 is addressed. Those that occur in the hardware spec are the following (linkcheck output):

(hw-spec/index: line   27) ok        https://datatracker.ietf.org/doc/html/rfc2119
(hw-spec/devices/datasheet: line   68) ok        https://en.wikipedia.org/wiki/Bit_field
(hw-spec/hierarchy: line   14) ok        https://en.wikipedia.org/wiki/Network_topology
(hw-spec/glossary: line  111) ok        https://en.wikipedia.org/wiki/Bus_(computing)

I feel these are acceptable.