Add separate x-enum-varnames tag

[rast1025]

Describe the PR
add separate tag for x-enum-varnames that supports arrays

Relation issue
https://github.com/swaggo/swag/pull/118/files

[codecov]

Codecov Report

Merging #1083 (ea33b4a) into master (4f32ae6) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head ea33b4a differs from pull request most recent head a9337d3. Consider uploading reports for the commit a9337d3 to get more accurate results

@@            Coverage Diff             @@
##           master    #1083      +/-   ##
==========================================
+ Coverage   94.19%   94.22%   +0.02%     
==========================================
  Files           9        9              
  Lines        2310     2321      +11     
==========================================
+ Hits         2176     2187      +11     
  Misses         70       70              
  Partials       64       64              

Impacted Files	Coverage Δ
field_parser.go	100.00% <100.00%> (ø)

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[ubogdan]

LGTM

[ubogdan]

@rast1025 Thanks for your contribution.