[FEAT]: Support GitHub organiaztion custom properties

[acouvreur]

Describe the need

Just like #1956 we should support custom properties for organization to be created.

It is also mentioned in #2316 test cases: https://github.com/integrations/terraform-provider-github/blob/main/github/data_source_github_repository_custom_properties_test.go#L13

TODO: at the time of writing org_custom_properties are not supported by this terraform provider, so cant be setup in the test itself for now

So this implementation could also fix that todo.

SDK Version

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API Version

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