Support FT.ADDHASH command

[dengliming]

A PR for #57

[codecov]

Codecov Report

Merging #62 into master will increase coverage by 0.04%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master      #62      +/-   ##
==========================================
+ Coverage   72.74%   72.78%   +0.04%     
==========================================
  Files          12       12              
  Lines        1108     1117       +9     
==========================================
+ Hits          806      813       +7     
- Misses        239      240       +1     
- Partials       63       64       +1     

Impacted Files	Coverage Δ
redisearch/client.go	79.61% <77.77%> (-0.05%)	⬇️

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[filipecosta90]

hi there @dengliming , can we include already the change in the README.md supported commands table?

[dengliming]

@filipecosta90 It was done. Thanks for your reviewing.

[filipecosta90]

@filipecosta90 It was done. Thanks for your reviewing.

Thanks @dengliming . Merging 👍