Implement inline palette spec parsing

include/gfx/pal_spec.hpp

@@ -0,0 +1,16 @@
+/*
+ * This file is part of RGBDS.
+ *
+ * Copyright (c) 2022, Eldred Habert and RGBDS contributors.
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#ifndef RGBDS_GFX_PAL_SPEC_HPP
+#define RGBDS_GFX_PAL_SPEC_HPP
+
+#include <string_view>
+
+void parseInlinePalSpec(char const * const arg);
+
+#endif /* RGBDS_GFX_PAL_SPEC_HPP */