Added ability to pass step amount for minutes value

[hamzahalhariri]

So the idea here is that i want to "add" or "take a way" a specific amount of minutes, basically add a jump steps
For example: add 15 mins every time i press on "arrow up" key when i have the caret on minutes group

const value = "12:00 AM"
<TimeInput value={value} step={15} onChange={onChange}/>
// expected the output when "key up" pressed
// while the caret is positioned in minutes group to be: "12:15 AM"

[codecov]

Codecov Report

Merging #8 into master will increase coverage by 0.22%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
+ Coverage   96.34%   96.57%   +0.22%     
==========================================
  Files          12       12              
  Lines         164      175      +11     
  Branches       49       51       +2     
==========================================
+ Hits          158      169      +11     
  Misses          5        5              
  Partials        1        1

Impacted Files	Coverage Δ
src/TimeInput.js	95.31% <100%> (+0.44%)	⬆️

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