Add example zombienet network file and instructions (#1839)

* Add simple example on how to spin up network.

* Update readme

* Remove unnecessary prefix

* Improve folder structure

* Add link to file

* Fix paths in readme

* Update README.md

Co-authored-by: Bastian Köcher <git@kchr.de>

Co-authored-by: Bastian Köcher <git@kchr.de>

zombienet/tests/runtime_upgrade.js

@@ -0,0 +1,24 @@
+const assert = require("assert");
+
+async function run(nodeName, networkInfo, args) {
+    const {wsUri, userDefinedTypes} = networkInfo.nodesByName[nodeName];
+    const api = await zombie.connect(wsUri, userDefinedTypes);
+
+    // get blockhash/runtimeVersion at block 1
+    const hashAtBlock1 = await api.rpc.chain.getBlockHash(1);
+    const versionAtBlock1 = await api.rpc.state.getRuntimeVersion(hashAtBlock1.toHuman());
+
+    // get blockhash/runtimeVersion at current head
+    const currentHeader = await api.rpc.chain.getHeader();
+    const hashAtCurrent = await api.rpc.chain.getBlockHash(currentHeader.number.toHuman());
+    const versionAtCurrent = await api.rpc.state.getRuntimeVersion(hashAtCurrent.toHuman());
+
+    const oldVersionIncremented = parseInt(versionAtBlock1.specVersion.toHuman(),10) + 1;
+    console.log("current", versionAtCurrent.specVersion.toHuman());
+    console.log("oldVersionIncremented", oldVersionIncremented);
+
+    // 2 == 2
+    assert.equal( oldVersionIncremented, versionAtCurrent.specVersion.toHuman(), "Running version should be the incremented version");
+}
+
+module.exports = { run }