Allow adopting of exitsting droplets

Description of your changes

Starts #66

This will allow the adopting of existing droplets into Crossplane so that users can bring their existing infra. I've also fixed the example and included an extra example for adopting an existing droplet.

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

Ran local cluster with kind, and adopted an existing resource. Also verified that it is not deleted when set to orphaned. Also verified that if an invalid ID is given it will error out and not continue.