DHT22: fix out of range problem and write doc

[undeadpelmen]

fix problem from previous pull request and write doc

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.6%. Comparing base (226f28b) to head (7a6479a).

Files with missing lines	Patch %	Lines
dht22/dht22.go	0.0%	4 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #112   +/-   ##
=====================================
  Coverage   52.6%   52.6%           
=====================================
  Files        117     117           
  Lines      11801   11802    +1     
=====================================
+ Hits        6205    6207    +2     
+ Misses      5232    5231    -1     
  Partials     364     364           

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[undeadpelmen]

pls check my doc, i from russia so my english not best