[Proposal] Support Archive instead of Delete in GitHub Repository

[Feggah]

What problem are you facing?

The deletion process of the repository is the same for other managed resources: Delete or Orphan. But, specially for GitHub Repos, there are some organizations that has some policies of instead of delete the repository, change it to Archived (that's the reality in my company).

How could Crossplane help solve your problem?

We should have an option for the deletion process that would archive the repository instead of deleting it.

Proposal

As discussed with @negz in the slack thread, we should have an optional parameter in the resource called deleteAction which is an Enum with the options Delete|Archive. This field will defaults to Delete.

The naming suggestion for this field was from @dgmorales

[Feggah]

Related to #13