Improve error messages, add changelog entry

distribution/changelog.txt

@@ -1,5 +1,6 @@
 0.4.31 (in development)
 ------------------------------------------------------------------------
+- Feature: [#25844] The sprite builder now also supports adding JSON-based palettes.
 - Improved: [#25765] The ‘View options’ and ‘Special track elements’ dropdowns no longer need click-and-hold.
 - Fix: [#4643, #25167] Many metal supports draw with a filled in top when they didn't in vanilla, causing some slight misalignment and glitching.
 - Fix: [#25739] Game freezes when a tab in the New Ride window contains more than 384 items.

src/openrct2/command_line/sprite/SpriteBuild.cpp

@@ -110,7 +110,7 @@ namespace OpenRCT2::CommandLine::Sprite
                     const auto image = SpriteImageLoad(imagePath, meta);
                     if (image == std::nullopt)
                     {
-                        fprintf(stderr, "Could not read image file: %s\nCanceling\n", imagePath.c_str());
+                        fprintf(stderr, "Could not read image file: %s\nCancelling\n", imagePath.c_str());
                         return -1;
                     }
                     images[imagePath] = image.value();

src/openrct2/drawing/ImageImporter.cpp

@@ -62,7 +62,7 @@ namespace OpenRCT2::Drawing
 
     PaletteImportResult ImageImporter::importJSONPalette(json_t& jPalette) const
     {
-        Guard::Assert(jPalette.is_object(), "ImageImporter::importJSONPalette expects parameter jPalette to be object");
+        Guard::Assert(jPalette.is_object(), "ImageImporter::importJSONPalette expects parameter jPalette to be an object");
 
         auto jColours = jPalette["colours"];
         auto numColours = jColours.size();