Fix kerning for SDF scaled fonts in font_manager.cpp (#3192)

Kerning is now also scaled with the scaled child font when using SDF fonts. In examples/common/font_manager.cpp kerning was visibly off when scaling SDF font down.

examples/common/font/font_manager.cpp

@@ -522,7 +522,9 @@ float FontManager::getKerning(FontHandle _handle, CodePoint _prevCodePoint, Code
 	if (isValid(cachedFont.masterFontHandle))
 	{
 		CachedFont& baseFont = m_cachedFonts[cachedFont.masterFontHandle.idx];
-		return baseFont.trueTypeFont->m_scale * stbtt_GetCodepointKernAdvance(&baseFont.trueTypeFont->m_font, _prevCodePoint, _codePoint);
+		return baseFont.trueTypeFont->m_scale 
+			* stbtt_GetCodepointKernAdvance(&baseFont.trueTypeFont->m_font, _prevCodePoint, _codePoint)
+			* cachedFont.fontInfo.scale;
 	}
 	else
 	{