docs/python: Point users at WebSocket

Users on Slack somewhat regularly ask questions around how to use the Python
bindings and finding quirks with it. Just for us to tell them they
should be using WebSockets instead. These might not be perfect, but at
least we're open to hear feedback and improve them, which isn't
necessarily our stance for the Python bindings.

Put up a big banner to redirect users into the future. Seems "warning" is
warranted given our reluctance and future ideas around deprecation for
the bindings.

doc/python.rst

@@ -4,6 +4,16 @@
 Python Bindings
 ===============
 
+.. warning::
+
+  To interact with Zeek, Broker's Python bindings should almost never be the
+  first choice nowadays. Consider them deprecated for most purposes. When setting
+  out to develop a new integration with Zeek, consider using :ref:`WebSockets <web-socket>`
+  instead. They avoid pitfalls during deployment and upgrades related to binary
+  compatiblity. For debugging purposes, the WebSocket protocol (in plaintext)
+  is easier to introspect and monitor on the wire, too.
+
+
 Almost all functionality of Broker is also accessible through Python
 bindings. The Python API mostly mimics the C++ interface, but adds
 transparent conversion between Python values and Broker values. In the