Add documentation and test for scriptId

Author: dozoisch

README.md

@@ -18,6 +18,7 @@ A React HOC for loading 3rd party scripts asynchronously. This HOC allows you to
     - `callbackName`: *string* : If the script needs to call a global function when finished loading *(for example: `recaptcha/api.js?onload=callbackName`)*. Please provide the callback name here and it will be autoregistered on `window` for you.
     - `globalName`: *string* : Can provide the name of the global that the script attaches to `window`. Async-script will pass this as a prop to the wrapped component. *(`props[globalName] = window[globalName]`)*
     - `removeOnUnmount`: *boolean* **default=false** : If set to `true` removes the script tag when component unmounts.
+    - `scriptId`: *string* : If set, it adds the following id on the script tag.
 
 #### HOC Component props
 ```js

test/async-script-loader-spec.js

@@ -139,6 +139,17 @@ describe("AsyncScriptLoader", () => {
     assert.equal(hasScript(URL), true, "Url in document");
   });
 
+  it("should add a id to the script tag", () => {
+    const URL = "http://example.com/?has_an_id=true";
+    const scriptId = "SOME_SCRIPT_ID";
+    const ComponentWrapper = makeAsyncScriptLoader(URL, { scriptId })(MockedComponent);
+    ReactTestUtils.renderIntoDocument(<ComponentWrapper />);
+
+    assert.equal(hasScript(URL), true, "Url in document");
+    const script = getScript(URL);
+    assert.equal(script.id, scriptId);
+  });
+
   it("should expose statics", done => {
     class MockedComponentWithStatic extends React.Component {
       static callsACallback(fn) {