Using zstd in kernel module

Hello, I am new to OpenWRT development. I am writing a netfilter kernel module for OpenWRT. I intend to do some compression in this module, for which I need zstd apis.
I see that this package is available as documented in OpenWRT website, but I cannot find any documentation about the apis exported by this package and if they are usable in kernel mode. Can someone please guide me through this.
Where Can I download the module to install and how do I use its apis?

Thank you,