Manual, section subcommands: add several tabs with Kotlin source code

[deining]

Time permitting, I will add more tabs with source code. So don't worry if you don't find time to recreate the html page immediately.

[remkop]

Merged. Thank you for the contribution!

[remkop]

The rendered HTML is also published now.

By the way, I noticed that the Kotlin highlighter has some trouble with things like

@Command(subcommands = [ A::class ]) // <--- notice the space between 'class' and `]` 
class X : Runnable

The space between 'class' and ] causes everything until 'X' to have red background.
Removing the space between ::class and the closing ] seems to fix it.
(Just FYI.)

[remkop]

And thanks again for the contributions! Shaping up very nicely!