Fix clippy warnings and add clippy ci check

[Skallwar]

• misc: Run clippy and fixes all warnings
• ci: Add clippy check

[codecov[bot]]

Codecov Report

Merging #168 (5409f49) into master (422b810) will increase coverage by 0.41%. The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #168      +/-   ##
==========================================
+ Coverage   64.32%   64.73%   +0.41%     
==========================================
  Files          17       17              
  Lines         625      621       -4     
==========================================
  Hits          402      402              
+ Misses        223      219       -4     

Impacted Files	Coverage Δ
src/disk.rs	0.00% <0.00%> (ø)
src/scraper.rs	23.07% <14.28%> (+0.37%)	:arrow_up:
src/downloader.rs	71.69% <80.00%> (+0.67%)	:arrow_up:
src/url_helper.rs	100.00% <100.00%> (ø)