Support for `.crt` files for CA roots

[vhavlena]

Heloo pgt-proxy team,

so-far the parameter --client-ca-roots-path assumes certificates to be .pem files only. Is it possible to extend it to consider also .crt files?

[galeaspablo]

Hey @vhavlena we're just keeping one format for now given how easy it is to convert .crt files to .pem before deploying. Although perhaps there's something I'm missing / a unique situation, where it's not feasible to do that?