fix(Viber): add type: 'keyboard' to the Keyboard type

[chentsulin]

#652

[codecov]

Codecov Report

Merging #654 (055e65d) into master (4bd5ebe) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #654   +/-   ##
=======================================
  Coverage   94.77%   94.77%           
=======================================
  Files          29       29           
  Lines        1781     1781           
  Branches      262      270    +8     
=======================================
  Hits         1688     1688           
  Misses         93       93           

Impacted Files	Coverage Δ
packages/messaging-api-viber/src/ViberTypes.ts	100.00% <ø> (ø)

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