Added a few to retrieve the channel number from Matterbridge's debug output.

Section-Telegram-(basic).md

@@ -5,3 +5,23 @@
 Token="Yourtokenhere"
 RemoteNickFormat="[{PROTOCOL}] <{NICK}> "
 ```
+
+## Retrieving your chat number from Matterbridge
+### Setup
+Matterbridge can output your chat number as debug information. Here's how.
+- Bring up a bot as described above and retrieve your API token. 
+ - Make to sure to disable privacy mode on the bot.
+- Configure Matterbridge as illustrated above
+- Join the bot to your Telegram group
+### Generate events / output
+- Start Matterbridge with your new configuration in debug mode like so: ``` matterbridge -debug -config matterbridge.toml```
+- Create traffic in your group, chat up your bot.
+- Matterbridge will output debug information, this will look similar to this
+```
+[0009] DEBUG telegram:     <= Message is config.Message{Text:"test from telegram", Channel:"-987654321", Username:"John Doe", UserID:"123456789", Avatar:"", Account:"telegram.mytelegram", Event:"", Protocol:"", Gateway:"", Timestamp:time.Time{wall:0x0, ext:> 0, loc:(*time.Location)(nil)}, ID:"31", Extra:map[string][]interface {}{}}
+```
+or
+```
+[0024] DEBUG telegram:     => Receiving config.Message{Text:"test from xmpp", Channel:"-987654321", Username:"[xmpp] <userredacted> ", UserID:"example@conference.redacted.com/userredacted", Avatar:"", Account:"xmpp.myxmpp", Event:"", Protocol:"", Gateway:"gateway1", Timestamp:time.Time{wall:0xbeed3ca55451a133, ext:24805708196, loc:(*time.Location)(0x55cad0c84140)}, ID:"", Extra:map[string][]interface {}(nil)}
+```
+- The large *negative* number in behind ```Channel:``` is your channel number. Go configure the Matterbridge gateway section with it.