Add discord.js to providers

[sudojunior]

• add discord.js to compatible queries
• add message 'cost' to command log
  • predetermined content length

calculateContentLength and debugContentLength are both available, the latter of which will colate lengths of all values that discord restricts

[sudojunior]

#73 can have discord.js support as confirmed

Warning

eris support is to be much more difficult with the current state of things and may require another rewrite with better abstraction as the main focus without being dependant on the docgen format.