Switch to modern build

Author: krassowski

.github/workflows/tests.yml

@@ -21,7 +21,7 @@ jobs:
         python-version: ${{ matrix.python-version }}
     - name: Install test dependencies
       run: |
-        python -m pip install --upgrade pip wheel
+        python -m pip install --upgrade pip wheel build
         python -m pip install -r requirements-dev.txt
     - name: Temporary installation
       run: python -m pip install -e .
@@ -33,7 +33,7 @@ jobs:
         mypy docstring_to_markdown
     - name: Build package
       run: |
-        python setup.py sdist bdist_wheel
+        python -m build
     - name: Install package
       run: python -m pip install --find-links=dist --no-index --ignore-installed docstring_to_markdown
     - name: Pip check