add pyside6 requirement

lukas-blecher#236 (comment)

Author: lukas-blecher

setup.py

@@ -10,6 +10,7 @@
 gui = [
     'PyQt6',
     'PyQt6-WebEngine',
+    'pyside6',
     'pynput',
     'screeninfo',
 ]
@@ -28,7 +29,7 @@
 
 setuptools.setup(
     name='pix2tex',
-    version='0.0.29',
+    version='0.0.31',
     description='pix2tex: Using a ViT to convert images of equations into LaTeX code.',
     long_description=long_description,
     long_description_content_type='text/markdown',