mdbook docs with i18n support with github action to upload source file to Crowdin and download translation

[krmanik]

I have used mdbook-i18n-helpers to add support for docs other than english language. Currently only crowdin target language .po file added in po directory.

• Files removed to setup for mdBook documentation.
• New theme was added using the command mdbook init --theme which included language picker, right-to-left (RTL) support, and keyboard navigation.
• Essential configuration files such as book.toml, Cargo.toml, dprint.json, .nojekyll, and .gitignore were added.
• Markdown formatting for AnkiDroid documentation is added (formatted using the dprint fmt tool), and the localization tool from AnkiDroid added to upload source messages.pot and download translated messages-*.po files.
• The initial languages (arabic, japanese, russian, chinese) were included, along with tools for automatic updates.
• If new translation added on crowdin Sync Translation action will download and update the translation.

Translation completed using Machine Translation of Crowdin.

Result
Documentation url with i18n support

• English
• Arabic
• Chinese
• Japanese
• Russian

Pull request created using Sync translation
https://github.com/krmanik/ankidroiddocs/pulls

Actions result
sync_translations
build
publish