docs(pushover): add basic documentation

docs/services/overview.md

@@ -6,7 +6,7 @@ Click on the service for a more thorough explanation.
 | -------------------------------------------- | ------------ |
 | [Discord](/shoutrrr/services/discord)                 | *discord://__`token`__@__`channel`__* |
 | [Telegram](/shoutrrr/services/not-documented)         | *telegram://__`token`__@telegram?channels=__`channel-1`__[,__`channel-2`__,...]* |
-| [Pushover](/shoutrrr/services/not-documented)         | *pushover://__`user`__:__`token`__@__`user`__/?devices=__`device`__* |
+| [Pushover](/shoutrrr/services/pushover)               | *pushover://shoutrrr:__`apiToken`__@__`userKey`__/?devices=__`device1`__[,__`device2`__, ...]* |
 | [Slack](/shoutrrr/services/not-documented)            | *slack://[__`botname`__@]__`token-a`__/__`token-b`__/__`token-c`__* |
 | [Email](/shoutrrr/services/not-documented)            | *smtp://__`username`__:__`password`__@__`host`__:__`port`__/?fromAddress=__`fromAddress`__&toAddresses=__`recipient1`__[,__`recipient2`__,...]* |
 | [Microsoft Teams](/shoutrrr/services/not-documented)  | *teams://__`token-a`__/__`token-b`__/__`token-c`__* |

docs/services/pushover.md

@@ -0,0 +1,28 @@
+# Pushover
+
+## URL Reference
+
+*pushover://shoutrrr:__`apiToken`__@__`userKey`__/?devices=__`device1`__[,__`device2`__, ...]*
+
+## Getting the keys from Pushover
+
+At your [Pushover dashboard](https://pushover.net/) you can view your __`userKey`__ in the top right.  
+![Screenshot 1](pushover/po-1.png)
+
+The `Name` column of the device list is what is used to refer to your devices (__`device1`__ etc.)
+![Screenshot 4](pushover/po-4.png)
+
+At the bottom of the same page there are links your _applications_, where you can find your __`apiToken`__
+![Screenshot 2](pushover/po-2.png)
+
+The __`apiToken`__ is displayed at the top of the application page.
+![Screenshot 3](pushover/po-3.png)
+
+## Optional parameters
+
+You can optionally specify the __`title`__ and __`priority`__ parameters in the URL:  
+*pushover://shoutrrr:__`token`__@__`userKey`__/?devices=__`device`__&title=Custom+Title&priority=1*
+
+__Note:__ Only supply priority values between -1 and 1, since 2 requires additional parameters that are not supported yet.
+
+Please refer to the [Pushover API documentation]() for more information.