Allow `padding` keyword for `Textbox`

[Datseris]

Feature description

Textbox brings a much needed feature to Makie: adding a text with surrounding box in the figure. It has all options necessary to style the textbox as you wish. Without Textbox, actually making text with a surrounding box can be very tedious and complex, and thus very hard to memorize, e.g., https://discourse.julialang.org/t/fill-a-bounding-box-behind-text-in-makie/101502/3.

The only thing I am misssing from Textbox is an additional padding argument, that controls the pad of the box borders themselves w.r.t. to their placement.

For plot types, please add an image of how it should look like

E.g., I have this nice figure:

where the labels top right are added with

        Textbox(fig[i, j];
            placeholder = string(round(rmi; sigdigits = 2)),
            textcolor_placeholder = :black, valign = :top, halign = :right,
            tellwidth = false, tellheight=false, boxcolor = (:white, 0.75),
            textpadding = (5, 5, 5, 5)
        )

where i, j iterates over the 10 axes locations. I would like to add an additional padding that would place the textbox futher away from the axis splines. textpadding controls the distance between text and the textbox borders so it is not that.

[jkrumbiegel]

You could use alignmode = Outside(padding)

[Datseris]

Fantastic, thank you. However, I do not understand the interaction between alignmodel = Outside(padding) and textpadding. For example, I have this setup:

            textpadding = (2, 2, 2, 2),
            alignmode = Outside(0, 5, 0, 5)

which does not align things properly and the text gets cut off:

while, without setting alignmode at all, the text very nicely fits into the box with the same textpadding keyword:

[jkrumbiegel]

Ah ok then the alignmode seems to take away space from the inside. Hm I have to think about it