Write README.md for fallback option

Author: hieuvp

README.md

@@ -230,11 +230,12 @@ componentDidMount() {
 }
 ```
 
-### `authenticate({ description })`: (iOS)
+### `authenticate({ description, fallbackEnabled })`: (iOS)
 Starts Fingerprint authentication on iOS.
 
 - Returns a `Promise`
 - `description: String` - the string to explain the request for user authentication.
+- `fallbackEnabled: Boolean` - display the fallback (Enter Password) button
 
 ```javascript
 componentDidMount() {

examples/yarn.lock

@@ -786,8 +786,8 @@ babel-types@^6.18.0, babel-types@^6.19.0, babel-types@^6.21.0, babel-types@^6.24
     to-fast-properties "^1.0.1"
 
 babylon@^6.13.0, babylon@^6.16.1, babylon@^6.17.2:
-  version "6.17.2"
-  resolved "https://registry.yarnpkg.com/babylon/-/babylon-6.17.2.tgz#201d25ef5f892c41bae49488b08db0dd476e9f5c"
+  version "6.17.3"
+  resolved "https://registry.yarnpkg.com/babylon/-/babylon-6.17.3.tgz#1327d709950b558f204e5352587fd0290f8d8e48"
 
 balanced-match@^0.4.1:
   version "0.4.2"