Add excludes in config lelvel, not only alerts yaml.

[Veres72]

Hello.
Could you add ignoring alerts by name or regexp via config file?
It will be nice for cases when there is no way to declare excludes in alerts declaration.
E.g we want to lint alerts in multitenancy cluster and send a notification to teams, which have alerts without time series. Teams are deploying their alerts as promerheusRules object and there is not possible to keep comments.

[prymitive]

Added ignore blocks to match - #81.
Plus there's a name field on match and ignore to allow matching by alert and record fields on prometheus rules.
Example:

rule {
    ignore {
        name = "Ignore .+"
    }
    ...
}

Would ignore this alert:

- alert: Ignore This Alert
  expr: sum(foo) > 0