[🙏] Selectively add namespaces instead of excludedNamespaces

[lukibahr]

Describe the user need
Instead of excluding namespaces via the excludedNamespaces: array, we would like to selectively add namespaces to a list, or choose namespaces by using label selectors, e.g.:

# Add selected namespaces
includedNamespaces:
  matchLabels: 
    key: value
#or 
includedNamespaces: 
  - namespaceA
  - namespaceB

Describe expected behaviour

snyk-monitor uses the exact list or selection of namespaces provided in the includedNamespaces field.

Additional context

Probably, the changes in the helm chart will not be that much, however, I don't know, if there are code-changes to be done.

[johnjelinek]

can we get a regex for this?