Update README.md

added How to find what reflectors are available

README.md

@@ -11,6 +11,8 @@ git clone https://github.com/n5amd/xlxd-debian-installer
 cd xlxd-debian-installer
 ./xlxd-debian-installer
 ```
+## How to find what reflectors are available
+Find a current active reflector dashboard, for example, https://xlx.n5amd.com/index.php?show=reflectors and you will see the gaps in reflector numbers in the list. Those reflector numbers not listed are available. 
 
 ### To interact with xlxd after installation:
 ```sh