Document the terraform provider available to automate reservations.

**Is your feature request related to a problem? Please describe.**
A full integration of the reservation functionality with Terraform is not allowed via script or data resources.

**Describe the solution you'd like**
We have implemented a terraform provider to interact with the Azure IPAM API for reservation management, available at https://registry.terraform.io/providers/XtratusCloud/azureipam/latest

**Additional context**
We consider it recommendable to include in the product documentation the availability of this terraform provider, so that it can be freely used by the end users, since it increases the application functionality.

NOTE; That the provider makes use of the functionality implemented to allow new tags to be added when making a reservation, and requested in the [issue 84](https://github.com/Azure/ipam/issues/84)