doc: Add Milesight EM300 TH (#1246)

* doc: Add Milesight EM300 TH

* doc: Edit per reviewer feedback

* doc: Update info about AppKey

doc/content/devices/models/milesight-em300-th/_index.md

@@ -0,0 +1,51 @@
+---
+title: "Milesight EM300-TH"
+description: ""
+weight: 
+---
+
+{{< figure src="milesight-EM300-TH.png" alt="Milesight EM300-TH" class="float plain" width="75%" >}}
+
+The [Milesight EM300-TH](https://www.milesight.com/iot/product/lorawan-sensor/em300-th) is an environment sensor suitable for monitoring indoor and outdoor temperature and humidity. It can be widely used in office areas, greenhouses and other environments.
+
+<!--more-->
+
+## Provisioning Information
+
+The provisioning information, **DevEUI**, can be found on the back of the device. You can use `24E124C0002A0001` as the **JoinEUI**. The **AppKey** will be received through an email after purchasing the device.
+
+{{< figure src="milesight-EM300-TH-back.png" alt="EM300-TH provisioning information" >}}
+
+{{< note "The Milesight EM300-TH cannot be onboarded to {{% tts %}} using QR code." />}}
+
+## Onboarding to {{% tts %}}
+
+You can onboard your EM300-TH using the **LoRaWAN Device Repository** or **manually** option.
+
+If you prefer onboarding with the **LoRaWAN Device Repository**, in the **End device type** section, under **Input method**, select the **Select the end device in the LoRaWAN Device Repository** option.
+
+The [Onboarding devices without QR codes]({{< ref "/devices/adding-devices/#onboarding-devices-without-qr-codes" >}}) section of the [Adding Devices]({{< ref "/devices/adding-devices/" >}}) guide explains this procedure in detail. Following details are EM300-TH-specific:
+
+- End device brand: **Milesight IoT Co., Ltd**
+- Model: **EM300-TH**
+- Hardware Ver.: **V2.2**
+- Firmware Ver.: **1.15**
+
+After configuring your device, select the **Register end device** button.
+
+{{< figure src="em300-th-device-repository.png" alt="Settings for registration through device repository" >}}
+
+If you prefer onboarding **manually**, in the **End device type** section, under **Input Method**, select **Enter end device specifics manually** option. The [Manually adding devices]({{< ref "/devices/adding-devices/manual/" >}}) and [Over the Air Activation (OTAA)]({{< ref "/devices/adding-devices/manual/otaa/" >}}) guides explain this procedure in detail. Following details are EM300-TH-specific:
+
+- LoRaWAN version: **LoRaWAN Specification 1.0.3**
+- Regional parameters version: **RP001 Regional Parameters 1.0.3 revision A**
+
+After configuring your device, select the **Register end device** button.
+
+{{< figure src="em300-th-manually.png" alt="Settings for manual registration" >}}
+
+## Monitoring Live Data
+
+When your device is registered, select the **Live Data** tab to view all messages exchanged between the end device and {{% tts %}}.
+
+{{< figure src="em300-th-live-data.png" alt="Live data tab" >}}