Build docs

[mardy]

• Build the opengx PDF file from the LaTeX source files.
• Remove the png images, since they can be rebuilt from the SVGs.
• Add a CI workflow to build the PDF documentation and publish it as an artifact.

[WinterMute]

Why is build-essential needed for building docs? Can we get rid of this?

Personally I'm not really a massive fan of installing software as part of any automated workflow, I think it's wasteful in terms of energy and network use and would prefer to avoid it if at all possible. Making a docker just for cmake, imagemagick and texlive-latex-extra is probably just as wasteful. Can this stuff be cached somehow?

[mardy]

Why is build-essential needed for building docs? Can we get rid of this?

It turns out we can, I removed it.

Personally I'm not really a massive fan of installing software as part of any automated workflow, I think it's wasteful in terms of energy and network use and would prefer to avoid it if at all possible. Making a docker just for cmake, imagemagick and texlive-latex-extra is probably just as wasteful. Can this stuff be cached somehow?

I'm not an expert on Github actions, so I'm not sure. But I now made a change to the action rules, so that the doc workflow starts only if some files under doc/ get modified. BTW, the workflow completes very quickly, so maybe it's not as resource intensive as it may seem.

[davidgfnet]

Nice! It is cool you plan on update the docs :)
LGTM!