Reference test HTML output

Author: adrhill

test/references/seismic_centered_html.txt

@@ -0,0 +1 @@
+<p><heatmap><heatmap-word style="background-color: #800000; color: white; padding: 0.2em; margin: 0.2em;">Test</heatmap-word><heatmap-word style="background-color: #8686FF; color: black; padding: 0.2em; margin: 0.2em;">TextHeatmaps</heatmap-word></heatmap></p>

test/runtests.jl

@@ -25,6 +25,7 @@ using Aqua
         @test h.colors[1] ≈ cmax
         @test h.colors[2] != cmin
         @test_reference "references/seismic_centered.txt" repr("text/plain", h)
+        @test_reference "references/seismic_centered_html.txt" repr("text/html", h)
 
         h = heatmap(val, words; rangescale=:extrema)
         @test h.colors[1] ≈ cmax