Add Royalties metadata view implementation.

[aishairzay]

Something to call out:

I named the env variable TOPSHOTROYALTYADDRESS. I did not find somewhere to set env variables per environment, but when being deployed this env variable should be set to the following per network: testnet b0aa0d8fa90ef9be mainnet faf0cc52c6e3acaf

Also worth noting that MetadataViews.getRoyaltyReceiverPublicPath() leads to a path that most probably does not have anything set up on the royalty receiving accounts. This is the path where the FTSwitchBoard (https://github.com/onflow/flow-ft/pull/71) should be setup to on some later date. This view is helpful regardless because it allows the address to be pulled out of the capability to help route the funds.