i18n(zh-cn): translate all untranslated files in the /learn

[KikkiZ]

What does this PR change?

• translate /learn/index.mdx
• translate /learn/sidecar-nodejs.mdx
• translate /learn/splashscreen.mdx
• translate /learn/system-tray.mdx
• fix rust code not being indented (/learn/system-tray.mdx)

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[KikkiZ]

last four commit added three untranslated files under /learn/Security