add readme.

Author: TatsunoriMorita

README.md

@@ -85,6 +85,7 @@ React Native date & time picker component for iOS, Android and Windows (please n
     - [`initialInputMode` (`optional`, `Android only`)](#initialinputmode-optional-android-only)
     - [`title` (`optional`, `Android only`)](#title-optional-android-only)
     - [`fullscreen` (`optional`, `Android only`)](#fullscreen-optional-android-only)
+    - [`showYearPickerFirst` (`optional`, `Android only`)](#showyearpickerfirst-optional-android-only)
     - [`onChange` (`optional`)](#onchange-optional)
     - [`value` (`required`)](#value-required)
     - [`maximumDate` (`optional`)](#maximumdate-optional)
@@ -534,6 +535,14 @@ List of possible values:
 <RNDateTimePicker fullscreen={true} />
 ```
 
+#### `showYearPickerFirst` (`optional`, `Android only`)
+
+If true, the date picker will open with the year selector first.
+
+```js
+<RNDateTimePicker showYearPickerFirst={true} />
+```
+
 #### `positiveButton` (`optional`, `Android only`)
 
 Set the positive button label and text color.