Merge pull request #539 from NordicSemiconductor/doc_green_led_dongle

doc: dongle: add info about LD2 green light

Author: greg-fer

doc/docs/programming_nrf52840_dongle.md

@@ -3,17 +3,18 @@
 To program the nRF52840 Dongle, complete the following steps:
 
 1. Open nRF Connect for Desktop and launch the {{app_name}}.
-2. Insert the nRF52840 Dongle into a USB port on the computer.
-3. Put the dongle into bootloader mode by pressing the **RESET** button.
+2. Insert the nRF52840 Dongle into a USB port on the computer.<br/>
+   The status light **LD2** turns on solid green, indicating that the dongle is powered up.
+3. Put the dongle into bootloader mode by pressing the **RESET** button.<br/>
 
     ![nRF52840 Dongle overview](./screenshots/nRF52840_dongle_press_reset.svg "Pressing the RESET button")
 
+    **LD2** starts pulsing red, indicating that the dongle is powered up and in the bootloader mode. After a few seconds, the computer recognizes the dongle as a USB composite device.
+
     !!! note "Note"
          - This step is not needed if the currently running application uses the [DFU trigger library](https://docs.nordicsemi.com/bundle/sdk_nrf5_v17.1.0/page/lib_dfu_trigger_usb.html), part of the nRF5 SDK v17.1.0.
          - If this is the first time the dongle is connected, a driver needed for the nRF52840 Nordic Secure DFU feature is also installed as part of this step.
 
-    The status light (**LD2**) will start pulsing red, indicating that the dongle is powered up and in bootloader mode. After a few seconds, the computer recognizes the dongle as a USB composite device.
-
 5. In the navigation bar in the {{app_name}}, click **Select device** and choose the serial number of the dongle from the drop-down list.
 6. Drag and drop the HEX file into the **File Memory Layout** section. Alternatively, click **Add file** to add the files you want to program, using one of the following options: