Update streamlabswater.markdown (#11983)

* Update streamlabswater.markdown

I didn't know about the API costs when I purchased the device, so this warning may help others make a more informed decision if they want to buy this product based on it's HA integration like I did.

* Moved warning from description to a note box

Wasn't sure if a note box, or a warning box was appropriate, so just used a normal note box. I also added a link to their subscription page instead of specifically listing the prices. That way if the prices change the docs don't need updated.

* Update streamlabswater.markdown

Fixed broken URL from previous edit

* ✏️ Tweak

Co-authored-by: Franck Nijhof <frenck@frenck.nl>

source/_integrations/streamlabswater.markdown

@@ -11,6 +11,12 @@ ha_iot_class: Cloud Polling
 
 The `Streamlabs Water` integration platform is used to interact with [Streamlabs water monitoring devices](https://www.streamlabswater.com/) in order to retrieve usage information and manage the away mode of the device. The [Streamlabs Water API](https://developer.streamlabswater.com) is used to retrieve daily, monthly, and yearly water usage along with the current away mode.
 
+<div class='note'>
+  
+Access to the StreamLabs Water API is not free, you must have a StreamPlus™ subscription level that enables API access. Visit [https://streamlabswater.com/subscription] for more information.
+
+</div>
+
 There is currently support for the following device types within Home Assistant:
 
 - Binary Sensor