test(vips): png filters palette, bitdepth, compression

* test(vips): png filters palette, bitdepth, compression

* test: update golden files

Author: cshum

testdata/golden/200x200/filters%3Aformat%28png%29%3Apalette%28%29%3Abitdepth%284%29%3Acompression%288%29/gopher.png

@@ -97,6 +97,7 @@ func TestProcessor(t *testing.T) {
 			{name: "proportion", path: "filters:proportion(10)/gopher.png"},
 			{name: "proportion float", path: "filters:proportion(0.1)/gopher.png"},
 			{name: "resize orient", path: "100x200/left/filters:orient(90)/gopher.png"},
+			{name: "png params", path: "200x200/filters:format(png):palette():bitdepth(4):compression(8)/gopher.png"},
 			{name: "fit-in unspecified height", path: "fit-in/50x0/filters:fill(white):format(jpg)/Canon_40D.jpg"},
 			{name: "resize unspecified height", path: "50x0/filters:fill(white):format(jpg)/Canon_40D.jpg"},
 			{name: "fit-in unspecified width", path: "fit-in/0x50/filters:fill(white):format(jpg)/Canon_40D.jpg"},