add "install and test" workflow

Author: simonhaenisch

.github/main.workflow

@@ -0,0 +1,15 @@
+workflow "Install & Test" {
+  on = "push"
+  resolves = ["npm test"]
+}
+
+action "npm install" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  runs = "install"
+}
+
+action "npm test" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  runs = "test"
+  needs = ["npm install"]
+}