github: add govulncheck action

[corverroos]

Adds a github action that executes vulncheck on every PR and every commit on main.

category: misc
ticket: #1368

[codecov]

Codecov Report

Base: 54.83% // Head: 54.81% // Decreases project coverage by -0.02% ⚠️

Coverage data is based on head (381630d) compared to base (0dff3de).
Patch has no changes to coverable lines.

❗ Current head 381630d differs from pull request most recent head 1db4e53. Consider uploading reports for the commit 1db4e53 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1714      +/-   ##
==========================================
- Coverage   54.83%   54.81%   -0.02%     
==========================================
  Files         160      160              
  Lines       20769    20769              
==========================================
- Hits        11389    11385       -4     
- Misses       7856     7860       +4     
  Partials     1524     1524              

Impacted Files	Coverage Δ
core/leadercast/transport.go	75.14% <0.00%> (-1.19%)	⬇️
app/app.go	63.39% <0.00%> (-0.72%)	⬇️
app/eth2wrap/synthproposer.go	66.25% <0.00%> (-0.32%)	⬇️
app/vmock.go	74.61% <0.00%> (+1.55%)	⬆️

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