add quick start to main html with code

[jkone27]

adds quick start to main html with code, sample for main idea, so that users have a quick way to start before diving into nested doc pages

[jkone27]

@Krzysztof-Cieslak probably this is not the best way to do this, but does it give the idea? let me know if i should change it or if u have quick suggestions, thank you so much fo Saturn 🪐 . prob something simple as adjusting the indentation and adapting colors would work, but maybe there is a way to have F# coloring/intellisense in the sample too?