Added caveat section to README

Let's tell people that BLE peripheral mode won't work on all devices

Author: beaufortfrancois

README.md

@@ -13,3 +13,10 @@ The developer can use the new Web Bluetooth features to connect to the app to Re
 From the app a developer can set the characteristics' values and send notifications.
 
 ![Battery Service](Battery Service.png) ![Heart Rate Service](Heart Rate Service.png)
+
+### Caveats
+
+BLE peripheral mode was introduced in Android 5.0 Lollipop. Due to hardware chipset dependency, some devices don't have access to this feature. Here's a non-exhaustive list of devices that support BLE peripheral mode at the time of writing: Nexus 6, Nexus 9, Moto E 4G LTE, LG G4, Galaxy S6.
+
+Source: http://stackoverflow.com/questions/26482611/chipsets-devices-supporting-android-5-ble-peripheral-mode
+