Clarify license

[martisak]

This repository is licensed under a GNU General Public License v2.0 license, and the repository includes output figures and tables generated by the script.

"The output of a program is not, in general, covered by the copyright on the code of the program. So the license of the code of the program does not apply to the output, whether you pipe it into a file, make a screenshot, screencast, or video." Source: https://www.gnu.org/licenses/gpl-faq.en.html#WhatCaseIsOutputGPL

The report (https://www.folkhalsomyndigheten.se/publicerat-material/publikationsarkiv/s/skattning-av-peakdag-och-antal-infekterade-i-covid-19-utbrottet-i-stockholms-lan-februari-april-2020/) contains the following text:

Bilder, fotografier och illustrationer är skyddade av upphovsrätten. Det innebär att du måste ha upphovsmannens tillstånd att använda dem.

which roughly translates to

Images, photographs and illustrations are protected by copyright. This means that you must have the author's permission to use them.