fix attributes search (monkey patch - part 2)

[t-bltg]

Fix https://github.com/JuliaPlots/Plots.jl/issues/2337. Fix https://github.com/JuliaPlots/PlotDocs.jl/issues/304. Fix https://github.com/JuliaPlots/PlotDocs.jl/issues/199.

As ugly as it might be, it works:

search_index.js

{"location":"generated/attributes_series.html","page":"Series Attributes","title":"Series Attributes","text":"These attributes apply to individual series (lines, scatters, heatmaps, etc) arrow bar_edges bar_position bar_width bins colorbar_entry connections contour_labels contours extra_kwargs fill_z fillalpha fillcolor fillrange fillstyle group hover label levels line_z linealpha linecolor linestyle linewidth marker_z markeralpha markercolor markershape markersize markerstrokealpha markerstrokecolor markerstrokestyle markerstrokewidth normalize orientation permute primary quiver ribbon series_annotations seriesalpha seriescolor seriestype show_empty_bins smooth stride subplot weights x xerror y yerror z z_order zerror","category":"page"}

Searching for show_empty_bins lands on attribute_series.html as first search result.

@BeastyBlacksmith, should we also add aliases ? ==> done