Add multiple block explorer support

[hewigovens]

Phantom wallet has a very nice feature to allow user choosing preferred block explorer

We can extend explorer in registry.json to include a list

[Milerius]

Thanks for opening the issue @hewigovens - explorer can became a list, codegen template CoinInfoData will need to be updated accordingly.

[hewigovens]

One more cool solana explorer: https://xray.helius.xyz/, would like to add https://mempool.space/ to Bitcoin too