Click and drag to create events (between blocks, modules, etc)

### Problem description
Current UX of creating events (i.e. 'links') between blocks in Policies requires users to navigate to both the source block and the destination block and via multiple clicks and drop-downs configure events in both. This is time consuming and cumbersome.

### Requirements
Implement the familiar click-n-drag method used in many drawing tools (e.g. draw.io) to connect the blocks. From source to destination with the dialogue popping to clarify event parameters at the end of the 'click-drag-release' sequence.

### Definition of done

- 'Click-n-drag' UX capability is implemented
- Documentation updated
- Users still able to configure events via navigating to blocks and selecting drop-downs etc (as is now)

### Acceptance criteria

- UX of creating events is improved to be intuitive with click-n-drag capability