Add typing to nvticache.py

[jjnicola]

No description provided.

[codecov]

Codecov Report

Merging #161 into master will increase coverage by 0.11%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #161      +/-   ##
==========================================
+ Coverage   71.17%   71.28%   +0.11%     
==========================================
  Files           4        4              
  Lines        1006     1010       +4     
==========================================
+ Hits          716      720       +4     
  Misses        290      290

Impacted Files	Coverage Δ
ospd_openvas/nvticache.py	96.39% <100%> (+0.13%)	⬆️

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