[doc][test] add 'args' to usage and add integration test

integration-test/Cargo.lock

@@ -0,0 +1,4 @@
+[[package]]
+name = "rust-action"
+version = "0.1.0"
+

integration-test/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "rust-action"
+version = "0.1.0"
+authors = ["Stefan Ruzitschka <icepuma@godda.mn>"]
+edition = "2018"
+
+[dependencies]

integration-test/src/lib.rs

@@ -0,0 +1,7 @@
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}