Include packages by default instead of excluding

[puddly]

We erroneously included docs as a submodule in the most recent couple of releases. src has been in there for a while too.

Instead of excluding folders, we instead just include the one module we expect to export.

---

The wheel itself has the expected folder structure now:

     serialx/__init__.py
     serialx/_serialx_rust.abi3.so
     serialx/async_serial.py
     serialx/common.py
     serialx/compat.py
     serialx/descriptor_transport.py
     serialx/py.typed
     serialx/serial.py
     serialx/serialutil.py
     serialx/platforms/__init__.py
     serialx/platforms/serial_darwin.py
     serialx/platforms/serial_esphome.py
     serialx/platforms/serial_extended_posix.py
     serialx/platforms/serial_freebsd.py
     serialx/platforms/serial_linux.py
     serialx/platforms/serial_posix.py
     serialx/platforms/serial_socket.py
     serialx/platforms/serial_win32.py
     serialx/platforms/serial_rfc2217/__init__.py
     serialx/platforms/serial_rfc2217/types.py
     serialx/tools/__init__.py
     serialx/tools/list_ports.py
     serialx/tools/list_ports_common.py
     serialx-1.4.1.dev1+g80949ea5c.dist-info/METADATA
     serialx-1.4.1.dev1+g80949ea5c.dist-info/WHEEL
     serialx-1.4.1.dev1+g80949ea5c.dist-info/top_level.txt
     serialx-1.4.1.dev1+g80949ea5c.dist-info/RECORD

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.48%. Comparing base (41e3829) to head (80949ea).
⚠️ Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev      #68   +/-   ##
=======================================
  Coverage   90.48%   90.48%           
=======================================
  Files          19       19           
  Lines        3143     3143           
=======================================
  Hits         2844     2844           
  Misses        299      299           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.