Add support for text bindings in workers

[blakeembrey]

From https://developers.cloudflare.com/workers/tooling/api/scripts/#add-a-secret-text-binding. It should be possible to upload a script with text and secret bindings included.

Expected behavior

Uploading a worker with bindings should support the new text and secret environment variable bindings.

Current behavior

It is not possible to upload text and secret bindings.

Possible solution

Add support for the two new bindings within the existing code path of UploadWorkerWithBindings

Context

I would really love to use Cloudflare Workers with terraform.

References

Links to any open or closed issues that may add context to this

• Terraform provider: https://github.com/terraform-providers/terraform-provider-cloudflare/issues/615
• Initial support: Add support for worker resource bindings #313.