We would love to have your contributions to Besu. The Start Here page has some basic info. In addition,
If you're even thinking about making any changes to Besu code, set up your github signoff so you don't have to worry about the DCO check.
If you're submitting a PR, you might need to add to the changelog.
If you're adding a new CLI option, take a look at the Besu CLI Style Guide.