Added pSTAKE and XPRT Tokens

[persistencedotone]

• Added token metadata for pSTAKE and XPRT
• Added pSTAKE and XPRT SVG logos
• pSTAKE Etherscan: https://etherscan.io/token/0xfb5c6815ca3ac72ce9f5006869ae67f18bf77006
• XPRT Etherscan: https://etherscan.io/token/0xD454b59f16D42667Be2fA55292d16647E27f40C4

[MRabenda]

Hey @persistencedotone could you please split this contribution to two separate PR - one per each token?

[persistencedotone]

Added two separate PRs pStake: https://github.com/MetaMask/contract-metadata/pull/1347 XPRT: https://github.com/MetaMask/contract-metadata/pull/1348