Add thebelab button to every code cell

[joergbrech]

Hi guys,

my jupyter book has pages that are getting quite long and I think it would be really convenient to add a thebelab button to every code cell. This way I don't have to scroll to the top if I sponateously decide I want to fiddle with a code block near the end of the page.

I tried implementing this, see for instance here (sorry, the page is in German...): https://joergbrech.github.io/Modellbildung-und-Simulation/00_einleitung/matlab_02_scripts_and_functions.html

I am happy to contribute this upstream if this seems like a feature that more people would use.