⚛️ Adjust spacing around cell outputs for better layout

[eleonorecharles]

Reduce the gap between a cell and its output ("A"), and increase the space between the next line and the cell output ("B") for improved readability.

Unsure whether this issue belongs to jupyter-ui or here.

[goanpeca]

Just looking at this @eleonorecharles this needs more discussion since the space between outputs is what is expected, the issue between input cell and outputs is that there is the three dot menu to the right that appears when there is a runtime connected and also the progress bar that appears when the klernel is busy. So this would require a bit more attention and planning.