docs(example, android): include logos in all example buttons

previously the continue buttons had logos, but sign in buttons did not
added them everywhere for consistency

Related #242

Author: mikehardy

example/app.android.js

@@ -168,20 +168,56 @@ export default RootComponent = () => {
             buttonStyle={AppleButton.Style.WHITE}
             buttonType={AppleButton.Type.SIGN_IN}
             onPress={() => doAppleLogin()}
+            leftView={(
+              <Image
+                style={{
+                  alignSelf: 'center',
+                  width: 14,
+                  height: 14,
+                  marginRight: 7,
+                  resizeMode: 'contain',
+                }}
+                source={appleLogoBlack}
+              />
+            )}
           />
           <AppleButton
             style={{ marginBottom: 10 }}
             cornerRadius={5}
             buttonStyle={AppleButton.Style.WHITE_OUTLINE}
             buttonType={AppleButton.Type.SIGN_IN}
             onPress={() => doAppleLogin()}
+            leftView={(
+              <Image
+                style={{
+                  alignSelf: 'center',
+                  width: 14,
+                  height: 14,
+                  marginRight: 7,
+                  resizeMode: 'contain',
+                }}
+                source={appleLogoBlack}
+              />
+            )}
           />
           <AppleButton
             style={{ marginBottom: 10 }}
             cornerRadius={5}
             buttonStyle={AppleButton.Style.BLACK}
             buttonType={AppleButton.Type.SIGN_IN}
             onPress={() => doAppleLogin()}
+            leftView={(
+              <Image
+                style={{
+                  alignSelf: 'center',
+                  width: 14,
+                  height: 14,
+                  marginRight: 7,
+                  resizeMode: 'contain',
+                }}
+                source={appleLogoWhite}
+              />
+            )}
           />
         </View>
       )}