docs: add README (#52)

README.md

@@ -1,3 +1,51 @@
 # RHOAS SDK for Go
 
-Go packages and API clients for RHOAS.
+[![Go Reference](https://pkg.go.dev/badge/github.com/redhat-developer/app-services-sdk-go.svg)](https://pkg.go.dev/github.com/redhat-developer/app-services-sdk-go)
+
+Go packages and API clients for RHOAS.
+
+## Prequisites
+
+- [Go 1.13](https://golang.org/doc/go1.13) or above
+
+## Installation
+
+Install the entire SDK with `go get`:
+
+```shell
+$ go get github.com/redhat-developer/app-services-sdk-go
+```
+
+```go
+import "github.com/redhat-developer/app-services-sdk-go"
+```
+
+Some APIs have their own modules, so you can `go get` the exact package you need:
+
+```shell
+$ go get github.com/redhat-developer/app-services-sdk-go/kafkamgmt
+```
+
+```go
+import "github.com/redhat-developer/app-services-sdk-go/kafkamgmt/apiv1"
+```
+
+## Supported APIs
+
+> NOTE: Some of these APIs are under development and may sometimes cause backwards-incompatible changes.
+
+
+| API                       | Status | Package |
+|---------------------------|--------|---------|
+| KafkaManagement           | beta |  [`github.com/redhat-developer/app-services-sdk-go/kafkamgmt/apiv1`](https://pkg.go.dev/github.com/redhat-developer/app-services-sdk-go/kafkamgmt/apiv1)      |
+| ServiceRegistryManagement | alpha  |  [`github.com/redhat-developer/app-services-sdk-go/serviceregistrymgmt/apiv1`](https://pkg.go.dev/github.com/redhat-developer/app-services-sdk-go/serviceregistrymgmt/apiv1)       |
+
+**Alpha**: the API is still being developed and may have backwards-incompatible changes. It is not recommended for production use.
+
+**Beta**: the API is mostly complete and stable, but still has outstanding features to be addressed. There may be minor backwards-incomptable changes.
+
+**Stable**: the API is ready for production use.
+
+## Contributing
+
+Contributions are welcome. See [CONTRIBUTING](CONTRIBUTING.md) for details.