Remove the space between inline/inline-block elements

[12rambau]

In one of my recent PR I realized that there were whitespaces in our primary sidebar (#965 ). The solution was simple, removed the prettifying step and keep inline tags on one single line.

Looking more carefully at our rendered pages I realize that we have trailing whitespaces everywhere.
It seems to be a more general problem as mentioned in this SO post: https://stackoverflow.com/questions/5078239/how-to-remove-the-space-between-inline-inline-block-elements

The "easy" fix is to rely on flexbox instead of inline-block whenever possible. If we do so we'll be able to keep the prettified html output AND avoid the trailing whitespaces.

I think we need to wait for the bootstrap 5 update as many of the display commands are comming from there:

• update to bootstrap 5 #953
• Split up bootstrap and theme css  #142

[12rambau]

we dropped prettify in #1101 that was not really necessary for production