Add mojo-dotenv to File Processing section

[Mjboothaus]

Hi,

I'd like to add mojo-dotenv to the File Processing section.

mojo-dotenv is a production-ready .env file parser for Mojo with 98%+ python-dotenv compatibility.

Key features:

• Variable expansion (${VAR} and $VAR)
• Multiline values with triple quotes
• Escape sequences (\n, \r, \t, \, ', ", \uXXXX)
• Auto-discovery (finds .env files in parent directories)
• 42 comprehensive tests

The package is:

• Available via modular-community (pending merge)
• Well-documented with usage examples
• Tested and production-ready
• Detailed blog post at https://www.databooth.com.au/posts/mojo/building-mojo-dotenv/

Repository: https://github.com/databooth/mojo-dotenv

Thanks for considering this addition!