Make @showprogress update on inner loop when using nested loops

I like the @showprogress macro very much, though I think it does not work well with nested loops. What I mean: I would expect the progress bar created with

@showprogress for j in 1:10, i in 1:10
    sleep(.1)
end

to behave exactly like

@showprogress for ij in 1:100
    sleep(.1)
end

, ie filling up with 1-percent increments. Instead, the progress bar from the first example fills up with 10-percent increments, ie is analogous to

@showprogress for j in 1:10
    for i in 1:10
        sleep(.1)
    end
end

I am not sure if this is possible, but I think in such cases it would be very nice to have the macro determine the overall number of iterations of the innermost loop in order to have less waiting time between updates.

Start by locating the @showprogress macro implementation and inspect how nested iteration is represented. Run the two nested-loop examples from the issue, then make the progress bar update in 1-percent increments like the single 1:100 loop and verify that behavior with the same examples.