fix: accept @angular v6 and later as peer

[tsvetomir]

PR Checklist

• [x] Read our contributing guidelines: https://github.com/progress/JSDO/blob/master/contributing.md#contribute-to-the-code-base.

The library doesn't seem to have issues with v9 at least although I haven't tested with v10 just yet.

As an alternative, the version range can be restricted, e.g. to 6-10.