Minor typos and formatting improvements in README.md

[Sumitds074]

Hi Zama team 👋

I’m a newcomer and noticed a few small wording and formatting things in the README that could improve clarity:

1. "Javascript API" → should be "JavaScript API" (capital S). Also ensure "WASM" is consistently capitalized throughout.
2. In the note about speeds, "best performances possible" could be adjusted to "best performance possible" (singular).
3. There seems to be a duplicate "About" section at the end of the file—maybe it could be removed to avoid redundancy.
4. (Optional) The Rust version note could mention how to check the version (e.g., rustc --version), which may help beginners.

These are small, non-code changes, but they should make the README a little clearer and more beginner-friendly.

Thanks for your work on TFHE-rs 🚀