/docs/reference/text/lowerおよび/docs/reference/text/upperの翻訳

[ultimatile]

text/lowerおよびtext/upperの翻訳です。

[Copilot]

Pull Request Overview

This PR translates the documentation for the text/lower and text/upper functions from English to Japanese. The changes include translating function descriptions, parameter documentation, and example section headers.

• Translates documentation comments for lower() and upper() functions from English to Japanese
• Updates translation status for both functions from "untranslated" to "translated"

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
website/translation-status.json	Updates translation status for /docs/reference/text/lower/ and /docs/reference/text/upper/ to "translated"
crates/typst-library/src/text/case.rs	Translates function documentation comments and parameter descriptions from English to Japanese

[ultimatile]

@kimushun1101 @3w36zj6
ありがとうございました。
最初の行は可能な限り体言止めにする方針だと認識しておりました。
「文字列やコンテンツを{小|大}文字に変換。」のようにしました。