Using backspace is prone to unexpected behavior

[fmaclen]

Using backspace it works fine as the user clears digits but when it clears a decimal point the formatting gets triggered immediately and the decimal point is removed automatically which causes the user to possibly accidentally remove an extra digit.

Approaches to try:

• Prevent formatting when using backspace altogether
• Add debouncing

Related to #13

[fmaclen]

This is probably was widely improved by #2, there may still be some funky behavior for some edge cases in which case a new issue should be opened with specifics.