Translating python-docs-theme

Hello!

The [Python docs Sphinx theme](https://github.com/python/python-docs-theme) now supports translation, but has not yet been translated to Bengali (India). You can find more on translating it in the [devguide.](https://devguide.python.org/documentation/translations/translating/#how-do-i-translate-the-python-docs-sphinx-theme)