Update setup.py.in

wheel/setup.py.in

@@ -19,6 +19,16 @@ Installing LALSuite from the Python Package Index requires pip >= 19.3.
 To install, simply run::
 
     $ pip install lalsuite
+
+Optional dependencies, which can be installed as ``pip install lalsuite[option]``:
+  * lalinference (pulls in
+    `gwdatafind <https://pypi.org/project/gwdatafind/>`
+     and `gwpy <https://pypi.org/project/gwpy/>`)
+  * lalpulsar (pulls in
+    `solar_system_ephemerides <https://pypi.org/project/solar-system-ephemerides/>`
+    which, until LALSuite 7.15, were still included in the main package)
+  * test (pulls in
+    `pytest <https://pypi.org/project/pytest/>`)
 """
 
 import os