Update README for localized files

Change-Id: I02a08e7a2b3f5ab28339c0e6bfa842e77608643d

Author: channing-google

LANGUAGES.md

@@ -0,0 +1,46 @@
+# Supported Languages
+
+| Code | Language |
+| ---- | -------- |
+| ar | Arabic |
+| bg | Bulgarian |
+| ca | Catalan |
+| zh_cn | Chinese (Simplified) |
+| zh_tw | Chinese (Traditional) |
+| hr | Croatian |
+| cs | Czech |
+| da | Danish |
+| nl | Dutch |
+| en | English |
+| en_gb | English (UK) |
+| fa | Farsi |
+| fil | Filipino |
+| fi | Finnish |
+| fr | French |
+| de | German |
+| el | Greek |
+| iw | Hebrew |
+| hi | Hindi |
+| hu | Hungarian |
+| id | Indonesian |
+| it | Italian |
+| ja | Japanese |
+| ko | Korean |
+| lv | Latvian |
+| lt | Lithuanian |
+| no | Norwegian (Bokmal) |
+| pl | Polish |
+| pt | Portuguese |
+| pt_pt | Portuguese (Portugal) |
+| ro | Romanian |
+| ru | Russian |
+| sr | Serbian |
+| sk | Slovak |
+| sl | Slovenian |
+| es | Spanish |
+| es_419 | Spanish (Latin America) |
+| sv | Swedish |
+| th | Thai |
+| tr | Turkish |
+| uk | Ukrainian |
+| vi | Vietnamese |

README.md

@@ -56,6 +56,28 @@ of your page, below the initialization snippet from the Firebase Console:
 <link type="text/css" rel="stylesheet" href="https://cdn.firebase.com/libs/firebaseui/2.1.1/firebaseui.css" />
 ```
 
+#### Localized Widget
+
+Localized versions of the widget are available through the CDN. To use a localized widget, load the
+localized JS library instead of the default library:
+
+```html
+<script src="https://www.gstatic.com/firebasejs/ui/2.1.1/firebase-ui-auth__{LANGUAGE_CODE}.js"></script>
+<link type="text/css" rel="stylesheet" href="https://www.gstatic.com/firebasejs/ui/2.1.1/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/2.1.1/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/2.1.1/firebase-ui-auth-rtl.css`, instead of the default
+stylesheet. The supported right-to-left languages are Arabic (ar), Farsi (fa), and Hebrew (iw).
+
+Internationalized binaries are currently not available in the GitHub repository due to dependencies
+on translation infrastructure that are not compatible with open sourced tools.
+
 ### Option 2: npm Module
 
 Install FirebaseUI and its dependencies via npm using the following command: