docs(grid): updating the README for the grid

[kdinev]

Closes #

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them

[Copilot]

Pull request overview

This PR updates the documentation for the grid component to reflect the correct import paths and improve filtering condition examples. The changes modernize the documentation to align with current best practices for tree-shaking and provide clearer, more practical examples.

Key changes:

• Updates import paths from igniteui-angular/grid to igniteui-angular/grids/grid
• Replaces the filtering conditions table with practical code examples showing operand classes
• Emphasizes per-package entry points for better tree-shaking

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.