Python 3.13 support

[layday]

👋 3.13 is still in alpha, but I thought I'd file this - in python/cpython#109113, get_unverified_chain was made public and calls public_bytes on the certs, meaning that

truststore/src/truststore/_api.py

Line 299 in 178fea2

cert_bytes = [cert.public_bytes(_ssl.ENCODING_DER) for cert in unverified_chain]

throws an error.

[sethmlarson]

@layday Thanks for reporting this, we'll update and get a new version published.

[layday]

(Typeshed PR: python/typeshed#11724)