I have a project that uses Kendo UI for jQuery to work with spreadsheets. I want to recreate the project from scratch in Angular using the Kendo UI for Angular Spreadsheet component.

In jQuery, I am currently using `kendo.spreadsheet.defineFunction()` (docs) to define our custom functions and I would like to do the same in Angular.

Allow the developer to customize the built-in Toolbar actions in Spreadsheet. Provide the ability to reorder or show only part of them:

Provide a readonly property to prevent the user from interacting with the data inside. 

Consider allowing the user to download the sheet.