Expand hitbox of 5 minute increment numbers

[jfkw]

This looks great. One difference from Android time input that was immediately noticeable was the high precision selection of minutes. With the mouse, I almost always get the exact nearest minute. With the native Android control, most taps select on a 5 minute increment, but individual minutes are selectable if you point carefully or drag.

react-timekeeper's control would feel a little more like that if the hitbox of 5 minute increments was somewhat larger that currently.

[catc]

Added in #19