Don't treat space and newline between Japanese/Chinese characters interchangeable

[tats-u]

Describe the bug

dprint-plugin-markdown version: 0.17.8

CSS requires line breaks in Japanese/Chinese text should be trimmed instead of converted to spaces.

https://drafts.csswg.org/css-text-4/#line-break-transform

EXAMPLE 16

這個段落是那麼長，
在一行寫不行。最好
用三行寫。

In languages that have no word separators, such as Chinese, “unbreaking” a line requires joining the two lines with no intervening space.

這個段落是那麼長，在一行寫不行。最好用三行寫。

Only Firefox follows this rule today.

https://wpt.fyi/results/css/css-text/line-breaking?label=master&label=experimental&aligned&q=segment-break-transformation-
https://drafts.csswg.org/css-text-4/#line-break-transform

Chrome & Safari's behavior is treated as a bug:

• https://issues.chromium.org/issues/40774934
• https://issues.chromium.org/issues/40069685
• https://bugs.webkit.org/show_bug.cgi?id=260857

Symbols for the following description:

• '字': Japanese or Chinese character (e.g. kanji/han, hiragana, and katakana)
• 'A': One of other characters (e.g. English and Korean)
• '\n': LF
• ' ': ASCII Space

Claims:

1. ' ' in '字' ' ' '字' should not be converted to '\n' but kept as is
2. '\n' in '字' '\n' '字' should be forcibly trimmed
3. ' ' or '\n' between '字' and 'A' can be processed by the current way (Prettier is going to forcibly convert it to ' ' but it's just due to the backward compatibility and dprint don't need to follow it)

You might want to see the following related issues/PRs in Prettier for details of backgrounds:

• Markdown: Disable breaking a line at the place around Chinese or Japanese characters even when proseWrap is always prettier/prettier#16710
• [For v3+ / breaking change] Should we change how to handle line breaking surrounded by han/kana when proseWrap is always prettier/prettier#14936
• Markdown: Don't break a line at the place around Chinese or Japanese characters prettier/prettier#16691
• [Frozen] Make Markdown's newline & space handling conform to web-platform-tests & Firefox's behavior prettier/prettier#15081

Input Code

日本語 日本語
日本語 日本語
日本語 日本語
English English
日本語 日本語
日本語 日本語
日本語 日本語
English English
日本語 日本語
日本語 日本語
日本語 日本語
English English

textWrap = always

Expected Output

日本語 日本語日本語 日本語日本語 日本語
English English
日本語 日本語日本語 日本語日本語 日本語
English English
日本語 日本語日本語 日本語日本語 日本語
English English

Actual Output

日本語 日本語 日本語 日本語 日本語 日本語 English English 日本語 日本語 日本語
日本語 日本語 日本語 English English 日本語 日本語 日本語 日本語 日本語 日本語
English English

https://dprint.dev/playground/#code/qemhpzR5UQBKYLAFDSuejrwKIDsDmAbAlgM4AWEWeRxK4SsCNa9kj5BJZObVTt1zyPFp0ocKJIA/config/N4KABGBEA2CWB2BTA6rAJgFwBaQFxgA4AGAGnCiQHcAZBRAaQTTymgDNIyJINEAPDMgBOAQwAOLSCOiURATwDOncpEQBbMVhELYCxvGb5IAVwOIhCgMYB7IYiVcoCjEOvwA5vsNRtvIboBrBxVYd3hbRAARWDtLDFgAN0RJNDF-eAwAWlDwu2VuHIiAMVhoKJjEOMTko1T0rMK7TLZS5MdIRsQAZQwRIQxo2PiklLSEBrCIzOc+jHyoToBRA0HK4ZqoOvHsyabEA0gQAF8QIA/plugin/markdown