use SPDX ID for license and make myself maintainer only

setup.py

@@ -30,10 +30,11 @@ def get_version():
     name='didjvu',
     description='DjVu encoder with foreground/background separation (Python 3 fork) ',
     version=get_version(),
-    license='GNU GPL 2',
+    license='GPL-2.0-only',
     long_description=(ROOT_DIRECTORY / 'README.rst').read_text(encoding='utf-8'),
     long_description_content_type='text/x-rst',
-    author='Jakub Wilk, FriedrichFröbel (Python 3)',
+    author='Jakub Wilk',
+    maintainer='FriedrichFröbel',
     url='https://github.com/FriedrichFroebel/didjvu/',
     packages=find_packages(
         where='.',
@@ -65,7 +66,7 @@ def get_version():
         'Development Status :: 4 - Beta',
         'Environment :: Console',
         'Intended Audience :: End Users/Desktop',
-        'License :: OSI Approved :: GNU General Public License (GPL)',
+        'License :: OSI Approved :: GNU General Public License v2 (GPLv2)',
         'Operating System :: OS Independent',
         'Programming Language :: Python',
         'Programming Language :: Python :: 3',