v0.5.0 - Adding Portworx Storage

Added

• Adds modular support for Storage providers. See https://github.com/equinix/terraform-metal-anthos-on-baremetal#storage-providers
• Adds Portworx as a storage provider that can be installed with the Terraform variable storage_module = "portworx"
• Installs common pre-requirements on worker nodes needed for various storage providers (lvm2)
• GitHub workflow for Terraform syntax and format validation

Fixes

• README typos