docs: update coverage badge to 87.80%

Update cumulative coverage from 87.8% to 87.80% for consistency.

Current coverage breakdown:
- Code coverage: 76.02%
- Type coverage: 99.58%
- Cumulative: 87.80%

Author: jdalton

README.md

@@ -2,7 +2,7 @@
 
 [![Socket Badge](https://socket.dev/api/badge/npm/package/@socketsecurity/sdk)](https://socket.dev/npm/package/@socketsecurity/sdk)
 [![CI](https://github.com/SocketDev/socket-sdk-js/actions/workflows/ci.yml/badge.svg)](https://github.com/SocketDev/socket-sdk-js/actions/workflows/ci.yml)
-![Coverage](https://img.shields.io/badge/coverage-87.8%25%20(test%2Btype)-brightgreen)
+![Coverage](https://img.shields.io/badge/coverage-87.80%25%20(test%2Btype)-brightgreen)
 
 [![Follow @SocketSecurity](https://img.shields.io/twitter/follow/SocketSecurity?style=social)](https://twitter.com/SocketSecurity)
 [![Follow @socket.dev on Bluesky](https://img.shields.io/badge/Follow-@socket.dev-1DA1F2?style=social&logo=bluesky)](https://bsky.app/profile/socket.dev)