Export Color debug functions

https://bugs.webkit.org/show_bug.cgi?id=294509
rdar://153407170

Reviewed by Eric Carlson.

I often want to use these from WebKit but when I do I get a linker failure.
This will fix the linker failure and prevent the need to rebuild everything
to enable the use of these useful functions.

* Source/WebCore/platform/graphics/Color.h:

Canonical link: https://commits.webkit.org/296382@main

Author: achristensen07

Source/WebCore/platform/graphics/Color.h

@@ -209,9 +209,9 @@ class Color {
         unsigned blue;
         unsigned alpha;
     };
-    DebugRGBA debugRGBA() const;
+    WEBCORE_EXPORT DebugRGBA debugRGBA() const;
 
-    String debugDescription() const;
+    WEBCORE_EXPORT String debugDescription() const;
 
 private:
     friend void add(Hasher&, const Color&);