Governance-sdk: bounties and referenda

[voliva]

I'll write some docs about this, but so far governance-sdk has two sub-sdks:

• Bounties
  • Loads descriptions of each bounty
  • Matches referenda related to the bounty
  • Looks for scheduled changes on the bounty status
  • Abstracts the different states into a TS-friendly interface
• Referenda
  • Inlines or wraps the proposal in a preimage as needed.
  • Resolves the proposal callData regardless if it's inline or in a preimage.
  • Decides best spender track for a specific value.
  • Provides approval/support curves as functions.
  • Calculates deciding + confirming period.