Support parimutuel markets

[saboonikhil]

A preview of events available on testnet:

• OutcomeBought: https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fbsr.zeitgeist.pm#/explorer/query/0x37f271a311c1a5ecdc5de5c4d3dc61c7cdc3056fd77b0898a2c715da0f2e779c
• ClaimRewards: https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fbsr.zeitgeist.pm#/explorer/query/0xf179188d5d7eff9e5aa1720c966167c08b615becac9a116da4012bdf27033d05
• BalanceRefunded: https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fbsr.zeitgeist.pm#/explorer/query/0xf179188d5d7eff9e5aa1720c966167c08b615becac9a116da4012bdf27033d05

cc: @maltekliemann 🙏