Add sample to mention a user on Teams.

Author: peombwa

samples/5-Chats.ps1

@@ -7,4 +7,17 @@ Get-MgChat
 Get-MgChatMessage -chatId $chatId 
 
 # Send a message in that 1:1 chat
-New-MgChatMessage -chatId $chatId -BodyContent "Hi from VSCode again!"
+New-MgChatMessage -chatId $chatId -BodyContent "Hi from VSCode again!"
+
+# Mention a user in a channel message.
+$UserToMention = Get-MGUser -UserId $userUPN
+
+New-MgTeamChannelMessage -ChannelId $ChannelId -TeamId $TeamId `
+    -BodyContentType "html" `
+    -BodyContent "Welcome to the channel! <at id='0'>$($UserToMention.DisplayName)</at>" `
+    -Mentions @( `
+        @{ `
+            id          = 0; `
+            mentionText = $UserToMention.DisplayName; `
+            mentioned   = @{user = $UserToMention } `
+        })