docs(CHANGELOG.md): 📚 add entry for context in line ranges and normalize list formatting
style(src/line_range.rs): 🎨 trim trailing whitespace in context parsing code
docs(long-help.txt): 📚 add examples for N::C and N:M:C context syntax
docs(clap_app.rs): 📚 update CLI help text with context syntax examples
feat(line_range.rs): ✨ implement N::C and N:M:C parsing and add tests
John Cavanaugh