Adjacent items with text decoration should be separated by a small gap

[r12a]

This issue is applicable to Chinese and Japanese.

When two underlined items appear side-by-side, the underline should be broken between the two. For example, although there are no gaps between characters in the code stream, there should be small visible gaps in the underlining of this Chinese example, which contains 2 proper nouns ('sòng', and 'ōuyángxiū') and a poem title ('míng fēi qū').

IFor more details, see this GitHub issue, which is being used to track this gap. Please add any discussion there, and not to this issue.

[r12a]

The first comment in this issue contains text that will automatically appear in one or more gap-analysis documents as a subsection with the same title as this issue. Any edits made to that comment will be immediately available in the Editor's draft of the document.

Please add any discussion to the GitHub issue being used to track this gap, and not to this issue