change type of $HomeServer to [uri]

this makes it more verbose what $HomeServer is and is
also technically the correct type for Invoke-RestMethod -Uri,
although we only use it concatinated there

bot.ps1

@@ -1,6 +1,6 @@
 param (
     [Parameter(Mandatory=$true)]
-    [string]
+    [uri]
     $HomeServer,
 
     [Parameter(Mandatory=$true)]