Clarify CJK font guidance

[ReinerBRO]

This updates the README to guide users toward system-installed fonts for non-Latin scripts instead of recommending the legacy CJK helper workflow.

Changes:

• replace the CJK font installation note with system-font guidance
• clarify that the CJK helper styles are legacy compatibility helpers
• update the Traditional Chinese example to show direct font selection

Validation:

• ... [100%]
  =============================== warnings summary ===============================
  ../../../miniconda3/lib/python3.13/site-packages/_pytest/config/init.py:1575
  /Users/h1syu1/miniconda3/lib/python3.13/site-packages/_pytest/config/init.py:1575: PytestConfigWarning: No files were found in testpaths; consider removing or adjusting your testpaths configuration. Searching recursively from the current directory instead.
  self.args, self.args_source = self._decide_args(

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
3 passed, 1 warning in 2.08s

[Kkkakania]

Thanks for putting this together. I checked the diff against #149: it replaces the old CJK font-installation recommendation with system-font + plt.rcParams["font.family"] guidance, and frames the cjk-* helper styles as legacy compatibility helpers. That matches the issue request from my read.

Small maintainer-facing suggestion: add Closes #149 to the PR body so the issue is linked/closed automatically if this is merged.