It's not exactly a "library" as such... but
Ian Coleman's BIP39 tool (written in Javascript) supports converting from BIP39 seed mnemonics into private/public keys and addresses for various address schemes (P2PKH, P2SH-P2WPKH, bech32 etc) using fully customisable derivation paths.
To get the "3"-type address that a Trezor seed would generate, you'd just select the "BIP49" tab in the middle of the page... and you should find the keys/addresses that match the ones generated by the Trezor. You may need to also change the "External/Internal" value from 0 to 1 to find "change" addresses.
You don't need to run this off his website either, as the full source is available for you to compile yourself and/or you can just download the standalone html page and run it offline.
Are you just wanting to recovery funds from a "lost" (or otherwise unavailable) device? or is this an ongoing need to want to be able to programmatically derive the private keys from the seed mnemonic? Either way, the website as it is should be able to help you recover funds... and the underlying javascript source code might help to understand the methods used to go from "seed mnemonic" -> "seed" -> "child key".