(#34) Remove issues.Filter()

[llorllale]

PR for #34:
Removed issues.Filter() and placed all configuration variables inside main package.

[codecov]

Codecov Report

Merging #35 into master will decrease coverage by 1.32%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #35      +/-   ##
=======================================
- Coverage   85.32%   84%   -1.33%     
=======================================
  Files           4     4              
  Lines         109   100       -9     
=======================================
- Hits           93    84       -9     
  Misses          8     8              
  Partials        8     8

Impacted Files	Coverage Δ
internal/issues/filters.go	86.66% <ø> (-3.08%)	⬇️

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