Align the RTC user menu dropdown in the top area

[jtpio]

A user menu dropdown is automatically added to the top area of the notebook when RTC is enabled:

This menu is currently a bit off and should be aligned vertically so it's more visually pleasing.

[jtpio]

Adding some pointers if anyone wants to have a look and open a PR.

The Notebook application should be started in collaborative mode with jupyter notebook --collaborative.

Then probably some CSS could be applied to that component, similar to the kernel logo also in the top area:

notebook/packages/notebook-extension/style/base.css

Lines 185 to 191 in e8e0f8f

	.jp-NotebookKernelLogo {
	flex: 0 0 auto;
	display: flex;
	align-items: center;
	text-align: center;
	margin-right: 8px;
	}

[stephenisau]

I can take a look at this ticket over the weekend if no one's claimed it yet.