update changelog and readme for v4.1.0 (#608)

Author: wti806

README.md

@@ -70,17 +70,17 @@ Localized versions of the widget are available through the CDN. To use a localiz
 localized JS library instead of the default library:
 
 ```html
-<script src="https://www.gstatic.com/firebasejs/ui/4.0.0/firebase-ui-auth__{LANGUAGE_CODE}.js"></script>
-<link type="text/css" rel="stylesheet" href="https://www.gstatic.com/firebasejs/ui/4.0.0/firebase-ui-auth.css" />
+<script src="https://www.gstatic.com/firebasejs/ui/4.1.0/firebase-ui-auth__{LANGUAGE_CODE}.js"></script>
+<link type="text/css" rel="stylesheet" href="https://www.gstatic.com/firebasejs/ui/4.1.0/firebase-ui-auth.css" />
 ```
 
 where `{LANGUAGE_CODE}` is replaced by the code of the language you want. For example, the French
 version of the library is available at
-`https://www.gstatic.com/firebasejs/ui/4.0.0/firebase-ui-auth__fr.js`. The list of available
+`https://www.gstatic.com/firebasejs/ui/4.1.0/firebase-ui-auth__fr.js`. The list of available
 languages and their respective language codes can be found at [LANGUAGES.md](LANGUAGES.md).
 
 Right-to-left languages also require the right-to-left version of the stylesheet, available at
-`https://www.gstatic.com/firebasejs/ui/4.0.0/firebase-ui-auth-rtl.css`, instead of the default
+`https://www.gstatic.com/firebasejs/ui/4.1.0/firebase-ui-auth-rtl.css`, instead of the default
 stylesheet. The supported right-to-left languages are Arabic (ar), Farsi (fa), and Hebrew (iw).
 
 ### Option 2: npm Module

changelog.txt

@@ -0,0 +1,2 @@
+feature - Included the ES module in `firebaseui` npm package.
+feature - Added the support of `login` custom parameter for `GitHub` provider.