feat: Add expandAll/collapseAll support

[MarcOrfilaCarreras]

This PR adds support for programmatically expanding and collapsing all nested tables.

Changes

• Added JSONGrid.prototype.expandAll
• Added JSONGrid.prototype.collapseAll
• Added README documentation for the new API methods
• Fixed README typos and improved wording

Example

var jsonGrid = new JSONGrid(data, container);

jsonGrid.render();

// Collapse all nested grids
jsonGrid.collapseAll();

// Expand all nested grids
jsonGrid.expandAll();

[araujoigor]

Thanks for the contribution (and for fixing the spelling mistakes :))

[araujoigor]

@MarcOrfilaCarreras maybe add some tests if you have the time. Should be easy to test your feature.

PS: I know I haven't added tests myself lol.

[MarcOrfilaCarreras]

@araujoigor Sorry for the delay. I’ve opened PR #37.