Suggestions to the gap analysis

[xfq]

Here are some suggestions to the gap analysis document. Any further comment is welcome!

---

Fonts:

I propose changing it from tbd to advanced.

One issue we might want to mention is that font matching/fallback for variation sequences is not implemented correctly: w3c/csswg-drafts#1710

---

Ruby annotation:

Mention the lack of support of Bopomofo ruby and difficulties selecting ruby text.

---

Text decoration:

Punctuations should be skipped by default for emphasis marks.

Emphasis & highlights:

It's related to text decoration. I propose changing it from ok to advanced.

---

Line breaking:

Browsers differ in how they handle line breaks for IDEOGRAPHIC SPACE (U+3000).

UAX #14 doesn't make sense for quotation marks in Chinese: https://www.w3.org/2018/05/14-clreq-minutes.html#x02

---

Counters, lists, etc.:

@counter-style is only supported in Firefox.

---

Page numbering, running headers, etc.:

We can use some text in the Hungarian Gap Analysis, since it applies to Chinese too:

Although there exist software that supports page numbers and running headers, none of the browsers do. Complex running headers (containing math, tables or other complex content) are not supported anywhere.

[ryukeikun]

OK for me.

[xfq]

Fixed in #182.