Add parser for i8

[Sh3Rm4n]

Needed for rust-netlink/wl-nl80211#26 to parse NL80211_SURVEY_INFO_NOISE, which is a signed value for the Noise in dBm

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 34.23%. Comparing base (ed3fc1b) to head (3c635cc).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/parsers.rs	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
- Coverage   35.08%   34.23%   -0.86%     
==========================================
  Files           3        3              
  Lines         362      371       +9     
==========================================
  Hits          127      127              
- Misses        235      244       +9     

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