[Doc] Add <TreeInput> and <ReferenceNodeInput> chapters

[fzaninotto]

import { Edit, SimpleForm, TextInput } from 'react-admin';
import { TreeInput } from '@react-admin/ra-tree';

export const ProductEdit = () => (
    <Edit>
        <SimpleForm>
            <TextInput source="id" disabled />
            <TextInput source="name" />
            <TreeInput source="category" treeData={[
                { id: 1, title: 'Clothing', isRoot: true, children: [2, 6] },
                { id: 2, title: 'Men', children: [3] },
                { id: 3, title: 'Suits', children: [4, 5] },
                { id: 4, title: 'Slacks', children: [] },
                { id: 5, title: 'Jackets', children: [] },
                { id: 6, title: 'Women', children: [7, 10, 11] },
                { id: 7, title: 'Dresses', children: [8, 9] },
                { id: 8, title: 'Evening Gowns', children: [] },
                { id: 9, title: 'Sun Dresses', children: [] },
                { id: 10, title: 'Skirts', children: [] },
                { id: 11, title: 'Blouses', children: [] },
            ]} />
        </SimpleForm>
    </Edit>
);

• Add TreeInput Chapter
• Add ReferenceNodeInput Chapter
• Mention new components in Reference and sidebar navigation
• Mention new components in related chapters