Support for scheduled object creation

[yunussandikci]

Hi 👋
This PR adds a new CRD called ScheduledResource which allows you to schedule an object creation in the future. It's an idea coming from a community member
You can also combine it with expire annotation, and basically mayfly will create and remove some objects only for a temprary time in the future.

Please feel free to share your opinion to make this PR better!

Example:

apiVersion: cloud.namecheap.com/v1alpha1
kind: ScheduledResource
metadata:
  annotations:
    mayfly.cloud.namecheap.com/expire: 60m
  name: example
  namespace: default
spec:
  in: 30m
  content: |
    apiVersion: v1
    kind: Secret
    metadata:
      name: example
      namespace: default
      annotations:
        mayfly.cloud.namecheap.com/expire: 30m
    data:
      .secret-file: dmFsdWUtMg0KDQo=
status:
  condition: Scheduled

Thanks!

cc @glourenco

[sandromodarelli]

you're a 🚀. i really like the implementation. maybe, before merging it, we can improve the documentation to have some human friendly explanation about how the ScheduledResource works. thank you for your great work 🙏

[glourenco]

I've edited the readme to add the ScheduledResource info

[eshepelyuk]

Curious if this going to be merged any time soon ?