add flat data grid to features list in docs (#120)

Author: RandomFractals

README.md

@@ -26,6 +26,7 @@ TODO: add a pic with simple data table, data summary and new flat data grid rend
 - View `CSV`, semi-flat `XML`, [`GeoJSON`](https://www.rfc-editor.org/rfc/rfc7946.html) and `JSON` **array** data Notebook 📓 cell ⌗ output in HTML table with column sort, number and date formatting
 - Incremental Data Table 🈸 rows creation on table scroll for faster display of larger datasets
 - [Data Summary 📊 Renderer View](https://github.com/RandomFractals/vscode-data-table#data-summary--renderer-view) for a quick overview of loaded dataset
+- [Flat Data 中 Grid Renderer](https://github.com/RandomFractals/vscode-data-table#flat-data-%E4%B8%AD-grid-renderer) with column summary headers, filtering, and `CSV` save options
 - Built-in [REST Book](https://github.com/RandomFractals/vscode-data-table#rest-book-example) 📓 [Python](https://github.com/RandomFractals/vscode-data-table#python-notebook-example) 🐍 [TypeScript Notebook](https://github.com/RandomFractals/vscode-data-table#typescript-notebook-example) 📓 [.NET Interactive Notebook](https://github.com/RandomFractals/vscode-data-table#net-interactive-notebook-example) 📓 and [Pyolite](https://github.com/RandomFractals/vscode-data-table#pyolite-notebook-example) 🐍 [Notebook Examples](https://github.com/RandomFractals/vscode-data-table#-examples) 📚
 - [Geo 🌐 Data Table 🈸 View](https://github.com/RandomFractals/vscode-data-table#geo--data-table--view)
 - Experimental [XML Data Table 🈸 View](https://github.com/RandomFractals/vscode-data-table#xml-data-table--view)