Tests/LibGfx: Add a JPEG XL test case using the Squeeze transform

The test case was created with:
`cjxl modular_property_8.jxl -d 0 -m 1 -R 1 modular_squeeze.jxl`

Author: LucasChollet

Tests/LibGfx/TestImageDecoder.cpp

@@ -2138,6 +2138,15 @@ TEST_CASE(test_jxl_modular_property_8)
     verify_checkerboard(*plugin_decoder);
 }
 
+TEST_CASE(test_jxl_modular_squeeze)
+{
+    auto file = TRY_OR_FAIL(Core::MappedFile::map(TEST_INPUT("jxl/modular_squeeze.jxl"sv)));
+    EXPECT(Gfx::JPEGXLImageDecoderPlugin::sniff(file->bytes()));
+    auto plugin_decoder = TRY_OR_FAIL(Gfx::JPEGXLImageDecoderPlugin::create(file->bytes()));
+
+    verify_checkerboard(*plugin_decoder);
+}
+
 TEST_CASE(test_jxl_icc)
 {
     auto file = TRY_OR_FAIL(Core::MappedFile::map(TEST_INPUT("jxl/icc.jxl"sv)));