No delete button for custom rules

[shahrzadav]

Is your feature request related to a problem? Please describe.
There is an option in the preference page of CogniCrypt that allows users to add local or remote rulesets. The problem is there is no button to delete or edit these. When too many rulesets are added, the preference page may crash.

Describe the solution you'd like
There could be a delete button next to the add custom rules button in the preference page that deletes the selected ruleset.

Additional context
We could also add an edit button in the future.