[fpc-pascal] Docs - structural change

[Michael Van Canneyt]

Hi,

It always bothered me that it is cumbersome to navigate the docs - the
standard tex4ht mechanism is too bare-bones.

So I added some postprocessing to add a (optional) sidebar:

https://www.freepascal.org/~michael/docs-demo/docs/sidebar/

Which makes navigation more comfortable.

It loads the sidebar at runtime with some javascript, to avoid bloating every page 
with the same sidebar HTML.

Comments, suggestions welcome.

(site might be slow currently, seems we're being visited by some bots...)

Michael.