chore: update lib.rs to include main rust docs content

[dutterbutter]

What 💻

• Move rust docs content from main.rs to lib.rs

Why ✋

• Since introducing lib.rs cargo doc will take lib.rs as the index.html file so I moved the content there so it can be rendered correctly.

Evidence 📷

Before:

After

Notes 📝

• Any notes/thoughts that the reviewers should know prior to reviewing the code?

[MexicanAce]

LGTM