heyoka 0.19.0

[bluescarni]

This new release focuses on cleanups, documentation and maintenance, as most of the development work for this release was focused on the Python bindings (https://github.com/bluescarni/heyoka.py).

The full changelog, as usual, is available here:

https://bluescarni.github.io/heyoka/changelog.html

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This discussion was created from the release heyoka 0.19.0.