feat: vote to change swap fee

[dckc]

refs:

• 9

• https://github.com/Agoric/documentation/issues/952

stacked on:

• 16

TODO:

• [x] set up a committee
• [x] wallet level test of voting, in addition to puppet governance
• [ ] e2e / on-chain testing

[Chris-Hibbert]

Thanks for sharing. This looks like good progress! I didn't see anything to improve.