[Typo] Standardize library name to "Rich" in README.ja.md

[r1tar]

• I've checked docs and closed issues for possible solutions.
• I can't find my issue in the FAQ.

In the installation section of README.ja.md, the library name was written as "リッチ" (katakana) but appears as "Rich" everywhere else in the document.　

- 以下のコマンドを実行して、ターミナルでリッチの出力をテストできます:
+ 以下のコマンドを実行して、ターミナルでRichの出力をテストできます:

[github-actions]

Thank you for your issue. Give us a little time to review it.

PS. You might want to check the FAQ if you haven't done so already.

Rich was created by Will McGugan. Consider sponsoring Will's work on Rich.

This is an automated reply, generated by FAQtory