Add PANOCpluc benchmarks

[aldma]

This PR adds the PANOCplus solver to the benchmarks.
The citation file has also been fixed (it could not be parsed).

[codecov]

Codecov Report

Merging #75 (abe28d1) into master (10d7e80) will not change coverage.
The diff coverage is n/a.

❗ Current head abe28d1 differs from pull request most recent head e6f9648. Consider uploading reports for the commit e6f9648 to get more accurate results

@@           Coverage Diff           @@
##           master      #75   +/-   ##
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  Coverage   88.93%   88.93%           
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  Files          21       21           
  Lines         886      886           
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  Hits          788      788           
  Misses         98       98           

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[lostella]

@aldma great, thanks! I'll merge this before #74 so that the benchmark runs there too