Add possibility to create an issue instead of a PR as remediation for blueprints

[netomi]

From OP:

I would like to use a regex in the content. This way i could restrict general parts of a file but open it for project specific parts using the regex pattern

[netomi]

Otterdog should observe the diff between a blueprint and a repo.

When there is a diff, it should, depending on a config flag;

• create a pr with a fix
• create an issue an reminder

This way a person who do not know about otterdog knows what to do.

The blueprint config might have fields for the issue/pr title and body.