Add requirements.txt

[lukasjenks]

Simple PR to add a requirements.txt file. Was in a fresh python venv so this should be all of the required ones. I noticed this snippet in site-packages/matplotlib/backends/backend_gtk4.py:

try:
    import gi
except ImportError as err:
    raise ImportError("The GTK4 backends require PyGObject") from err

So while pygobject isn't required unless you're running on a GTK4 backend, the error produced when hit if it's missing sometimes doesn't help much without some digging, since it's triggered by the gi.require_version() call instead of the try/catch above if you have a different gi module installed. So may as well include pygobject in the requirements.txt file for GTK4 users.

  File "<python venv path>/python3.11/site-packages/matplotlib/backends/backend_gtk4agg.py", line 4, in <module>
    from . import backend_agg, backend_gtk4
  File "<python venv path>/python3.11/site-packages/matplotlib/backends/backend_gtk4.py", line 19, in <module>
    gi.require_version("Gtk", "4.0")
    ^^^^^^^^^^^^^^^^^^
AttributeError: module 'gi' has no attribute 'require_version'

(Error comes from site-packages/matplotlib/backends/backend_gtk4.py if running a UI based on GTK4 like me).

[braindotai]

Perfect ;)