Improved user experience in the OCaml Documentation Tutorials

[yashi-hub]

Issue Description

I have changed the layout for OCaml Manual.
these changes include fixing the right-div at the time of scrolling.

Fixes # (issue)
I have fixed the layout of all the pages relating to OCaml manual.
This PR fixes the issue ocaml/ocaml.org#1402

I have also described the changes I have made in the form of a video here

WhatsApp.Video.2021-04-19.at.1.08.55.PM.mp4

• Please check if the PR fulfills these requirements

• PR is descriptively titled and links the original issue above
• Before/after screenshots (if this is a layout change)
• Details of which platforms the change was tested on (if this is a browser-specific change)
• Context for what motivated the change (if this is a change to some content)

[yashi-hub]

hey, @patricoferris @avsm,
it would be great if you could review this PR so that I can make all the required changes as fast as possible.
thankyou :))