API doc - add CONSTANTS section


#1

Suggest adding a CONSTANTS section containing the well-known pre-defined constants and #defines already in the Blinks core and lib’s (and moving the couple already mentioned in CONVENIENCE section). E.g. SERIAL_NUMBER_LEN
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#2

This sounds like a nice addition to the docs. Added your suggestion and will expose ones that seem user friendly and helpful. Of course they can all be found in the source, but it is helpful to know which ones are most desired by game designers/developers.