Make sidebar sticky (on Opam Docs Website)

[MisterFISHUP]

Hi,

I wanted to bring up an issue with the current Opam Docs website. The sidebar on the doc pages isn't sticky, and I believe making it sticky would improve the user experience.

I'm not quite sure which code or repository I need to modify to make this change and submit a pull request. To give a better idea of what I mean, I've attached a screenshot that shows the changes I made directly in the devtools.

Thanks for your help!

opam-sticky-sidebar.mp4

[rjbou]

It would be great, indeed!
For the ocaml code creating the bar, it is here

opam2web/src/o2wDocumentation.ml

Lines 127 to 134 in 1ec15cb

	Html.div ~cls:"row"
	(Html.div ~cls:"span3"
	(Html.div ~cls:"bs-docs-menu hidden-phone"
	(doc_menu
	@ Html.div ~cls:"bs-docs-toc" html_toc))
	@ Html.div ~cls:"span9"
	(header
	@ Cow.Html.of_string (Omd.to_html md_content)))

For the style, CSS are defined in https://github.com/ocaml-opam/opam2web/tree/master/ext/css