Add New Fields

[tomhschmidt]

From @willwarren89

Description
Support additional metadata in the relayer registry.

Motivation and Context
Relayers may choose to include additional metadata associated with their web or mobile app to the relayer registry. Ideally, the new metadata can be used to add search filters in 0x Portal increasing discoverability by allowing users to find relayers that satisfy a distinct set of requirements.

Fields to include:
[x] language support: include array of supported language subtages ("en" "kr" "fr")
[ ] platform: {web, mobile: {native, toshi, status, trustwallet, ...}}
[ ] key management: {metamask, ledger, trezor, parity signer, ...}
[ ] relayer model: {open orderbook, matching, p2p, ...}
[ ] market category: {ICOs, securities, collectibles, debt assets, prediction markets: {sports, esports, politics, stocks}, ...}
[ ] supported trading pairs or tokens?
[ ] permissions?
[ ] Twitter + social media handles