stop-words 0.10.1

This patch fixes language-feature combinations and adds a non-panicking lookup API while retaining Rust 2021 and the existing get() function.

• Add lookup(), available_languages(), the Language enum, and the all convenience feature.
• Deprecate LANGUAGE with a warning to use Language. Existing enum and variant imports continue to work; both enum types are generated from a shared definition.
• Fix feature combinations that hid existing enum variants and support builds with no language data.
• Preserve published ISO/NLTK lists and NLTK source precedence; remove only the duplicate Klingon vaj entry.
• Correct package metadata, include the Apache license text, and update documentation, examples, and CI coverage.

Migration: replace LANGUAGE with Language. Existing get() calls remain supported. Use lookup() when a language may be unknown or disabled; it returns None instead of panicking.

Validation covers all eight data-feature combinations, Rust 1.84, legacy enum imports and warnings, strict Clippy/rustdoc, package verification, and comparison against published data.