feat: create 'Grid' model and 'grid' component

[ximenesyuri]

Description

To create Grid model and grid component. Grid model should be composed of Rows (create a model for that). Rows, in turn, should be composed of Cells.

from typed import optional, Str, ...

@optional
class Cell:
    cell_id: Str
    cell_class: Str
    cell_style: Str
    cell_level: Int
    cell_inner: Any

@optional
class Column:
    col_id: Str
    col_class: Str
    col_style: Str
    col_cells: List(Cell)
Col = Column

@optional
class Grid:
    grid_id: Str
    grid_class: Str
    grid_style: Str
    grid_cols: List(Column)