add setting unicast bit

[XiXiangFiles]

Description:

for the unicast bit issue
I just rebase to the latest. previous pr: https://github.com/mafintosh/dns-packet/pull/49

related issues

https://github.com/mafintosh/dns-packet/issues/21

[codecov-commenter]

Codecov Report

Merging #96 (ab17088) into master (7b66620) will increase coverage by 0.01%. The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##           master      #96      +/-   ##
==========================================
+ Coverage   97.99%   98.00%   +0.01%     
==========================================
  Files           6        6              
  Lines        2046     2057      +11     
==========================================
+ Hits         2005     2016      +11     
  Misses         41       41              

Files	Coverage Δ
index.js	98.08% <100.00%> (+0.01%)	:arrow_up:

[silverwind]

See https://github.com/mafintosh/dns-packet/pull/94#issuecomment-1807954392

[XiXiangFiles]

@silverwind thx for your reviewing. I modify it to qu from QU. Thank you for continuing to leave comments on the Pull Request from many years ago