Adding support for Trufflehog V3

[JulianGR]

The new-ish Trufflehog V3 needs rules in YAML format as specified here: https://docs.trufflesecurity.com/docs/configuration/detectors/

Just as a note, this is a sample new rules file:

detectors:
- name: generic-api-key
  keywords:
  - key
  - api
  - token
  - secret
  - client
  - passwd
  - password
  - auth
  - access
  regex:
    generic-api-key: "(?i)([sample regex]?:]|$)"

I updated the convert-rules.py so that it now accepts trufflehogV2, gitleaks and the new trufflehogV3. Those rules can now be used with the latest release of trufflehog just using the flag --config /path/to/config.yml, being the config.yml the file that the convert-rules.py script outputs.

I also updated the readme for clarification (the current readme has the usage commands in LaTeX format somehow...) and because the old --type trufflehog is now separated in --type trufflehogv2 and --type trufflehogv3 respectively.

Keep up the good work =)