[docs] Enable Bengali at the language switcher dropdown

[fellyph]

This pull request adds quick access for the Bengali language. The most significant changes include updating the Docusaurus configuration to include Bengali, improving the Japanese language label, and making formatting adjustments to the new Bengali documentation.

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screenshot:

Localization Improvements:

• Added Bengali (bn) as a supported locale in the Docusaurus configuration, including a label in Bengali script and a dedicated path.
• Updated the Japanese locale label from "Japanese" (in English) to "日本語" (in Japanese script) in the Docusaurus configuration.

Bengali Documentation Adjustments:

• Added a formatting fix and removed unnecessary admonition markers in the Bengali translation of the code contribution guide (code.md). [1] [2]