webhook has emoji now (#207)

[clsung]

• implements one feature request of Messaging API - May 2020 update #207

[kkdai]

LGTM.

[nasa9084]

LGTM, please rebase to resolve conflict

[codecov-commenter]

Codecov Report

Merging #208 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #208      +/-   ##
==========================================
+ Coverage   76.85%   76.87%   +0.01%     
==========================================
  Files          31       31              
  Lines        2320     2322       +2     
==========================================
+ Hits         1783     1785       +2     
  Misses        434      434              
  Partials      103      103              

Impacted Files	Coverage Δ
linebot/emoji.go	100.00% <ø> (ø)
linebot/event.go	88.16% <100.00%> (+0.14%)	⬆️
linebot/message.go	77.56% <100.00%> (ø)

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