Adding GHCR.io Support

[davidcollom]

This add's support for GHCR.io, allowing the use of the Github Personal Access token.

[JoshVanL]

/lgtm

[JoshVanL]

/approve

[jetstack-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: davidcollom, JoshVanL

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