v21

refactor: restructure demo components and remove unused files

- Removed demo-fileinput and demo-time components along with their associated HTML, SCSS, and TypeScript files.
- Updated demo-datetime module to include necessary imports and declarations for NgxMatDatetimepicker.
- Cleaned up home component to reflect the removal of demo components and updated links.
- Adjusted shared module to properly declare NgxMatHighlightDirective.
- Updated Karma configuration to use coverage-istanbul-reporter.
- Modified TypeScript configuration for better module resolution and compatibility.
- Removed TSLint configuration as part of the migration to ESLint.