fix: handle self-signed CA into Vouch proxy

[lerminou]

fixes: vouch/vouch-proxy#145

Allow to add internal self-signed CA into the container
In our company we have a internal Keycloak OIDC and we need to add our certificate.

create a new image from the official and extend is not our best option because we don't want to maintain every new version

[halkeye]

can you update it to be 3.3.0? (probably 3.4 cause I think i might merge #33 first)