feat: add support and example for secure webhook feature

[brpat07]

Fixes

Adding support and example for the feature of secure webhook

Checklist

• I acknowledge that all my contributions will be made under the project's license
• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the Contribution Guidelines and my PR follows them
• I have titled the PR appropriately
• I have updated my branch with the master branch
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation about the functionality in the appropriate .md file
• I have added inline documentation to the code I modified

If you have questions, please file a support ticket, or create a GitHub Issue in this repository.

[codecov]

Codecov Report

Merging #389 into master will increase coverage by 0.09%.
The diff coverage is 77.77%.

@@            Coverage Diff             @@
##           master     #389      +/-   ##
==========================================
+ Coverage   72.47%   72.57%   +0.09%     
==========================================
  Files           3        4       +1     
  Lines         476      485       +9     
==========================================
+ Hits          345      352       +7     
- Misses        127      128       +1     
- Partials        4        5       +1     

Impacted Files	Coverage Δ
helpers/securewebhook/securewebhook.go	77.77% <77.77%> (ø)

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[anujs3]

good work @brpat07! this LGTM, but should we add a unit test for getting the public key?

[brpat07]

good work @brpat07! this LGTM, but should we add a unit test for getting the public key?

I haven't added any code related to getting the public key, other then the example; so it does not make sense to add the unittest for that.

[eshanholtz]

LGTM