Subscriptions: How to "Listen" for Events and What to do ...

[nelsonic]

In order to have "Event Listeners" (so users can hit the [Enter] Key to create a Todo Item #55) We need to add "Subscriptions" to Elm(ish). see: https://www.elm-tutorial.org/en/03-subs-cmds/01-subs.html

Todo

• [x] investigate/research if we need to register events each time the DOM is re-rendered
• [x] write a test for subscriptions ... e.g:
  • [x] [Up] & [Down] keyboard key press increases/decreases the counter.
• [x] add subscriptions parameter to mount function
• [x] invoke the subscriptions in mount depending on the outcome of initial research

required for: https://github.com/dwyl/learn-elm-architecture-in-javascript/issues/55

[nelsonic]