Add crypto library and CI

The crypto library is a simple way to manage x509 certificates that will be used by DFSS modules.

It is able to:

- Create private keys
- Create self-signed root certificates
- Create certificate requests
- Create certificates from requests
- Keys and certificates are exported/imported in PEM format

See merge request !3

Add CONTRIBUTING.md



See merge request !1

Update README to add workspace configuration



See merge request !2