[DOCS] Add how to generate terraform documentation

[rblcoder]

Add steps to generate terraform provider documentation to README.md

[prudhvigodithi]

Do you mean to add a step to run tfplugindocs to generate and validate provider documentation?
Thanks

[rblcoder]

@prudhvigodithi I thought of adding the following to README.md to generate documentation
go generate ./...
as per https://developer.hashicorp.com/terraform/tutorials/providers-plugin-framework/providers-plugin-framework-documentation-generation