Support character-spacing in span tag

Support character-spacing in span tag

Add Character-Spacing value attribute "char-space-value" to span tag.

How to apply it in TextEditor:

   textEditor.SetProperty(Dali::Toolkit::TextEditor::Property::TEXT,
                           "<span font-size='20' font-family='DejaVu Sans' font-width='condensed' font-slant='italic' text-color='blue' >ABC EF\n</span>"
                           "<span font-size='20' font-family='DejaVu Sans' font-width='condensed' font-slant='italic' text-color='red' char-space-value='-5.0f'>ABC EF\n</span>"
                           "<span font-size='20' font-family='DejaVu Sans' font-width='condensed' font-slant='italic' text-color='green' char-space-value='10.0f'>ABC EF\n</span>");
   textEditor.SetProperty(Dali::Toolkit::TextEditor::Property::ENABLE_MARKUP, true);

This patch should be preceded by the patch below:
https://review.tizen.org/gerrit/c/platform/core/uifw/dali-toolkit/+/271789

Change-Id: I203c6e1f3a116ae557ffbc84859a121739e6b6c6