README: what's this fork (#76)

Add description of what this fork is about, clarify where to contribute and where to find docs.
Point badges to information about this fork.

README.md

@@ -1,13 +1,10 @@
 # SCION
 
+[![SCIONLabDocs](https://img.shields.io/badge/docs-SCIONLab-blue)](https://docs.scionlab.org)
 [![Documentation](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white)](https://pkg.go.dev/github.com/scionproto/scion)
 [![ReadTheDocs](https://img.shields.io/badge/doc-reference-blue?version=latest&style=flat&label=docs&logo=read-the-docs&logoColor=white)](https://anapaya-scion.readthedocs-hosted.com/en/latest)
-[![Build Status](https://badge.buildkite.com/e7ca347d947c23883ad7c3a4d091c2df5ae7feb52b238d29a1.svg?branch=master)](https://buildkite.com/scionproto/scion)
-[![Go Report Card](https://goreportcard.com/badge/github.com/scionproto/scion)](https://goreportcard.com/report/github.com/scionproto/scion)
-[![GitHub issues](https://img.shields.io/github/issues/scionproto/scion/help%20wanted.svg?label=help%20wanted&color=purple)](https://github.com/scionproto/scion/issues?q=is%3Aopen+is%3Aissue+label%3A%22help+wanted%22)
-[![GitHub issues](https://img.shields.io/github/issues/scionproto/scion/good%20first%20issue.svg?label=good%20first%20issue&color=purple)](https://github.com/scionproto/scion/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22)
-[![Release](https://img.shields.io/github/release-pre/scionproto/scion.svg)](https://github.com/scionproto/scion/releases)
-[![License](https://img.shields.io/github/license/scionproto/scion.svg?maxAge=2592000)](https://github.com/scionproto/scion/blob/master/LICENSE)
+[![Go Report Card](https://goreportcard.com/badge/github.com/netsec-ethz/scion)](https://goreportcard.com/report/github.com/netsec-ethz/scion)
+[![License](https://img.shields.io/github/license/netsec-ethz/scion.svg?maxAge=2592000)](https://github.com/netsec-ethz/scion/blob/scionlab/LICENSE)
 
 Welcome to the open-source implementation of
 [SCION](http://www.scion-architecture.net) (Scalability, Control and Isolation
@@ -17,25 +14,31 @@ isolation, and explicit trust information for end-to-end communication. To find
 out more about the project, please visit our [documentation
 site](https://anapaya-scion.readthedocs-hosted.com/en/latest/).
 
-## Connecting to the SCION Test Network
+## SCIONLab / this fork
 
 Join [SCIONLab](https://www.scionlab.org) if you're interested in playing with
-SCION in an operational global test deployment of SCION. As part of the SCIONLab
-project, we support [pre-built binaries as Debian
-packages](https://docs.scionlab.org/content/install/).
+SCION in an operational global test deployment of SCION.
 
-## Building
+This fork of [scionproto/scion](github.com/scionproto/scion), specifically the
+branch `scionlab`, is the version of SCION running in
+[SCIONLab](https://www.scionlab.org).
+Our version moves in a roughly biannual release cycle behind the upstream
+master, which is an attempt to find a balance between the cutting edge and
+periods of protocol and API stability. 
+We typically maintain a few SCIONLab specific quirks here. Occasionally, we
+include an experimental feature before it becomes available upstream.
 
-To find out how to work with SCION, please visit our [documentation
-site](https://anapaya-scion.readthedocs-hosted.com/en/latest/contribute.html#setting-up-the-development-environment)
-for instructions on how to install build dependencies, build and run SCION.
+## Building / Contributing
 
-## Contributing
+As part of the SCIONLab
+project, we support [pre-built binaries as Debian
+packages](https://docs.scionlab.org/content/install/).
 
-Interested in contribution to the SCION project? Please visit us at
-[contribute.rst](https://anapaya-scion.readthedocs-hosted.com/en/latest/contribute.html)
-for more information about how you can do so.
+Please contribute directly upsteam at [scionproto/scion](github.com/scionproto/scion) 
+when possible; have a look at the 
+[setup instructions](https://anapaya-scion.readthedocs-hosted.com/en/latest/build/setup.html)
+and the [contribution guide](https://anapaya-scion.readthedocs-hosted.com/en/latest/contribute.html).
 
 ## License
 
-[![License](https://img.shields.io/github/license/scionproto/scion.svg?maxAge=2592000)](https://github.com/scionproto/scion/blob/master/LICENSE)
+[![License](https://img.shields.io/github/license/netsec-ethz/scion.svg?maxAge=2592000)](https://github.com/netsec-ethz/scion/blob/scionlab/LICENSE)