Get rid of getting started frictions

[SimonDanisch]

• Give a clear choice of backends in the docs (make sure error message when not loading a backend also gives a clear, consistent choice) make the backend choice more clear #4040
• GLMakie should default to activate!(; inline=false, float=true). There have been multiple reports of people not even realizing that GLMakie is interactive since it was only displayed as a PNG in the plot-pane and people have also been reporting, that the GLMakie window is hard to find under some OS window managers (e.g. osx).
• Remove MakieGallery from JuliaHub/JuliaPlots (@pfitzseb, https://docs.juliahub.com/MakieGallery/Ql23q/0.2.17/basic-tutorial.html). - [ ] Make sure that https://github.com/JuliaPlots/MakieGallery.jl is not the first google result (currently it is for Makie gallery). Not sure what we need to do for that, maybe remove the repository entirely?

Feel free to add simple to solve items to this list. Bigger getting started frictions, either in scope or because there needs to be a larger discussion on what to do about it, should be discussed somewhere else.