Publish TS types

[gohabereg]

Publish typescript types to DefinitelyTyped repository or to own organization on npmjs.org

[gohabereg]

Following the typescript documentation it is better to include declaration files to the package.

We have types definition for EditorJS class and some definitions for Tools. For now I think it's better to just store everything in @editorjs/editorjs package.

So if you need to implement BlockTool interface you need to install core package:

import {BlockTool} from '@editorjs/editorjs';

class MyTool implements BlockTool {

}