node-gyp is no longer needed; clicking on group titles toggles the selection

[XimitGaia]

Proposed Changes

• The node-sass dependency package has been replaced by sass so that node-gyp is no longer needed.
• The prop withGroupClick was implemented. It allows click on group titles to toggle the selection of group items.

[liorheber]

Hi,

Thank you very much for your contribution. You seem to be adding multiple features under the same pull request which I rather we avoid to ensure we can easily review, test and rollback each change.

I didn't go over the whole PR due to that but a few quick comments -

1. This change requires an upgrade of the node version the project uses.
2. extracting the style to an external css is a breaking change and should be treated as such.

I'm happy to see through these changes but if you want to push them, please split this PR into separate PRs, each introducing a singular feature or change and we can review and merge them one by one.

Thanks again!