feat: Add on_add_row event for grid in Dialog

[marination]

Documentation: https://frappeframework.com/docs/user/en/api/dialog?editWiki=1&wikiPagePatch=aj13edb2n0

• Add an event on_add_row to a grid that is not inside a form (eg. in a dialog)
• This can be used to manipulate data and add presets to the dialog grid dynamically

Usage:

const dialog = new frappe.ui.Dialog({
	title: __("Create Logs"),
	fields: [
		{
			fieldname: "logs",
			fieldtype: "Table",
			label: __("Logs"),
			in_place_edit: true,
			reqd: 1,
			fields: table_fields,
			// set data on row addition, idx = visible idx of the row
			// set `log_type` as alternating IN/OUT in dialog table on row addition
			on_add_row: (idx) => {
				let data_id = idx - 1;
				let logs = dialog.fields_dict.logs;
				let log_type = (data_id % 2) == 0 ? "IN" : "OUT";

				logs.df.data[data_id].log_type = log_type;
				logs.grid.refresh();
			},
		},
	],
	primary_action: (values) => {},
	primary_action_label: __("Create"),
});