Add description, license and package requirements

LICENSE

+MIT License
+
+Copyright (c) 2023 Françoise CONIL
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+

README.md

+# Get PyPI packages backends
+
+Get Python packages backends found in `pyproject.toml` files with the
+`build-backend` key from [PyPI](https://pypi.org/).
+
+This could be done thanks to [Querying every file in every release on the Python Package Index](https://sethmlarson.dev/security-developer-in-residence-weekly-report-18)
+from Seth Michael Larson.
+

requirements.in

+duckdb
+urllib3
+matplotlib
+pandas

requirements.txt

+#
+# This file is autogenerated by pip-compile with Python 3.10
+# by the following command:
+#
+#    pip-compile requirements.in
+#
+contourpy==1.2.0
+    # via matplotlib
+cycler==0.12.1
+    # via matplotlib
+duckdb==0.9.2
+    # via -r requirements.in
+fonttools==4.46.0
+    # via matplotlib
+kiwisolver==1.4.5
+    # via matplotlib
+matplotlib==3.8.2
+    # via -r requirements.in
+numpy==1.26.2
+    # via
+    #   contourpy
+    #   matplotlib
+    #   pandas
+packaging==23.2
+    # via matplotlib
+pandas==2.1.3
+    # via -r requirements.in
+pillow==10.1.0
+    # via matplotlib
+pyparsing==3.1.1
+    # via matplotlib
+python-dateutil==2.8.2
+    # via
+    #   matplotlib
+    #   pandas
+pytz==2023.3.post1
+    # via pandas
+six==1.16.0
+    # via python-dateutil
+tzdata==2023.3
+    # via pandas
+urllib3==2.1.0
+    # via -r requirements.in