Add note explaining the historical python-snap7 name

The library no longer wraps the C snap7 library as of 3.0, but the name
is kept for backwards compatibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gijzelaerr

README.rst

@@ -3,6 +3,10 @@ About
 
 Python-snap7 is a pure Python S7 communication library for interfacing with Siemens S7 PLCs.
 
+The name "python-snap7" is historical — the library originally started as a Python wrapper
+around the `Snap7 <http://snap7.sourceforge.net/>`_ C library. As of version 3.0, the C
+library is no longer used, but the name is kept for backwards compatibility.
+
 Python-snap7 is tested with Python 3.10+, on Windows, Linux and OS X.
 
 The full documentation is available on `Read The Docs <https://python-snap7.readthedocs.io/en/latest/>`_.

doc/introduction.rst

@@ -6,6 +6,11 @@ natively with Siemens S7 PLCs. The library implements the complete S7
 protocol stack including TPKT (RFC 1006), COTP (ISO 8073), and S7
 protocol layers.
 
+The name "python-snap7" is historical: the library originally started as a
+Python wrapper around the `Snap7 <http://snap7.sourceforge.net/>`_ C library.
+As of version 3.0, the C library is no longer used, but the name is kept for
+backwards compatibility.
+
 python-snap7 requires Python 3.10+ and runs on Windows, macOS and Linux
 without any native dependencies.