Add a "Whirldwind Tour" to the guide

[Technius]

This is a WIP PR to add a "Whirlwind Tour" to the guide, similar to the brief introduction in the current guide on the wiki.

[Technius]

I've been occupied with other things recently so any help here would be welcome.

[rolandlo]

In general I pretty much like the whirldwind tour. Pdf annotation and export to pdf/svg/png should definitively be featured more prominently though. While describing how to create different shapes (which is also important), please do also briefly mention the shape recognizer.
Don't hesitate to add more pictures, as that will help the novice to find things and make the reading more comfortable.

I agree with the overview, giving the user the choice to take the whirldwind tour or to look for more specific topics.

[Technius]

I updated the whirlwind tour just now. I pruned out much of the detail that I originally planned to include, as the whirlwind guide should be a sort of 5-10 minute tutorial that demonstrates bare minimum functionality.

I would like to see this merged sooner rather than later. It should not take very much effort to amend the guide in the future.

[rolandlo]

Looks nice to me. Good job with the icons. I only have minor comments.

[rolandlo]

I'm not quite sure, if this is correctly understood in case of a stylus.

[Technius]

I've clarified this section.

[Technius]

Thanks for the feedback. I inserted more icons and added the LaTeX tool to the tool table.

[rolandlo]

LGTM. Please go ahead and merge.