Pull Request type

Please add the labels corresponding to the type of changes your PR introduces:

Description

It adds the mainnet endpoint, update the avail-js docs, has few optimizations.

[x] I have performed a self-review of my own code.
[x] The tests pass successfully with cargo test.
[x] The code was formatted with cargo fmt.
[x] The code compiles with no new warnings with cargo build --release and cargo build --release --features runtime-benchmarks.
[x] The code has no new warnings when using cargo clippy.
[x] If this change affects documented features or needs new documentation, I have created a PR with a documentation update.