feat: 🎸 Group/Nested Data Handling

[SaiFi0102]

Handles nested data like:

[
	{
		"_isGroup": 1,
		"rows": [...rows (can handle nested group objects)...],
		"totals": {...field1: x, field2: y...}
	},
	...
]

And creates either a tree view or empty-row-separated groups list view

Tree View

Empty-Row-Separated Groups List View