Leverage built-in fetch API (remove axios)

[dlackty]

This pull request removes the axios dependency in favor of the built-in fetch API.

• Reduced bundle size: Eliminates the need for an external library.
• Improved compatibility: Enables usage in environments like Cloudflare Workers and Vercel Functions, which often have limited library support.
• Modernization: Aligns with the growing adoption of fetch API in Node.js. Node.js 16 reaching end-of-life, and the later versions since Node.js 18 have fetch API built-in.

[laurynas]

Dear @dlackty, thank you for your valuable contribution!

I have incorporated it into v3.0.0 release:
https://github.com/detectlanguage/detectlanguage-node/releases/tag/v3.0.0