docs: fix typos in README.md

[hungdinh82]

Description

1. “XTMP” is incorrect. XMTP is a decentralized messaging protocol commonly used in Web3.
2. “somehwere” is a misspelling; the correct spelling is “somewhere.”

Tests

Checklist

• [ ] I have formatted and linted my code
• [ ] All new and existing tests pass
• [ ] My commits are signed (required for merge) -- you may need to rebase if you initially pushed unsigned commits

[cb-heimdall]

🟡 Heimdall Review Status

Requirement	Status	More Info
Reviews	🟡 0/1	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1

[vercel[bot]]

@hungdinh82 is attempting to deploy a commit to the Coinbase Team on Vercel.

A member of the Team first needs to authorize it.