Gets or sets the html rendering of the cells in the range.
True to make the cell render the value as HTML.
It is important to sanitize the value of the cell on the server for passing safe html because there is no client-side sanitizing. When editing a cell the new value can be checked and prevented in the client
When the value is 'true ' the value of the cell should be always sanitized on the server for passing safe html.
Boolean the current html state of the top-left cell of the range.