Feat/bind plus

[yyjjqq94]

support like:
hotkeys('ctrl-y, ctrl-a', {splitKey: '-'}, function(e){
console.log('you press bind keys')
})

Close #104

[codecov-io]

Codecov Report

Merging #105 into master will increase coverage by 2.29%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master    #105      +/-   ##
=========================================
+ Coverage    83.9%   86.2%   +2.29%     
=========================================
  Files           1       1              
  Lines         174     174              
=========================================
+ Hits          146     150       +4     
+ Misses         28      24       -4

Impacted Files	Coverage Δ
dist/hotkeys.js	86.2% <0%> (+2.29%)	⬆️

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[coveralls]

Pull Request Test Coverage Report for Build 175

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+2.4%) to 73.298%

---

Totals
Change from base Build 173:	2.4%
Covered Lines:	150
Relevant Lines:	174

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💛 - Coveralls

[jaywcjlove]

@yyjjqq94 thx!

[madfriend]

Great, thanks!