docs: fix README wording and typos

[AdekunleBamz]

What

• Fixes small grammar/casing issues in README for clarity and consistency (e.g., “a TRON”, “JustLend”, “TRC20”, “Node.js”, “macOS”).
• Keeps URLs and behavior unchanged; this is documentation-only.

Why

• Makes the README more professional and easier to follow for new users.

Changes

• README.md: brand casing consistency (“JustLend”), grammar (“a TRON”), TRC20 wording (“TRC20-compliant”, “TRC20”), and minor terminology cleanup (“Node.js”, “macOS”).

PR link

• https://github.com/AdekunleBamz/justlend-protocol/pull/new/docs/readme-typos