Add a workflow for running tests

.github/main.workflow

@@ -0,0 +1,15 @@
+workflow "CI" {
+  on = "push"
+  resolves = "Test"
+}
+
+action "Dependencies" {
+  uses = "actions/npm@v2.0.0"
+  args = "ci"
+}
+
+action "Test" {
+  needs = "Dependencies"
+  uses = "actions/npm@v2.0.0"
+  args = "test"
+}