doc: add links to INSTALLED_APPS facilities

Author: phycodurus

docs/api/tom_observations/facilities.rst

@@ -37,4 +37,16 @@ Blanco
 ******
 
 .. automodule:: tom_observations.facilities.blanco
-    :members:
+    :members:
+
+
+********************************
+Facilities as ``INSTALLED_APPS``
+********************************
+
+The following Facilities are implemented as ``INSTALLED_APPS``. As such,
+each resides in its own git repository:
+
+* `Neil Gehrels Swift Observatory (tom_swift) <https://github.com/TOMToolkit/tom_swift>`__
+* `European Southern Observatory (tom_eso) <https://github.com/TOMToolkit/tom_eso>`__
+* `Liverpool Telescope (tom_lt) <https://github.com/TOMToolkit/tom_lt>`__