feat(ui-components): implement events for number input

[remmycat]

Notes:

• I tried writing tests for the other events too, but simulating the mouse and change events got rather complex - I couldn't get it working in the test environment. (I tried this: https://modern-web.dev/docs/test-runner/commands/#send-keys )
• I added the type hints for the properties because I noticed the number conversions weren't happening without them, which broke my code. The other code just always converted everything that might be a string into a number / boolean. I removed those explicit conversions, since this would sweep invalid types under the rug otherwise. With the type hint lit will convert the values for us.

Ticket: #481