docs: Update docs/src/user_docs/stdlib/main.md with new modules

[This table](https://0xmiden.github.io/miden-vm/user_docs/stdlib/main.html#available-modules) (docs/src/user_docs/stdlib/main.md) needs to be updated. For example, we should mention `std::collections::smt` and `std::crypto::hashes::rpo` modules here as well (maybe some other modules too). 

_Originally posted by @bobbinth in https://github.com/0xMiden/miden-vm/pull/2103#discussion_r2332102937_
            