Add: Undocumented "Reference Tag Update" event

[n-thumann]

What

This PR adds the (undocumented) "Reference Tag Update" event. According to NVD this event is expected, but yet to be documented (see linked ticket).

Why

To be able to handle events like https://services.nvd.nist.gov/rest/json/cvehistory/2.0?eventName=Reference%20Tag%20Update.

References

https://jira.greenbone.net/browse/VTA-495

Checklist

• Tests

[github-actions]

Conventional Commits Report

Type	Number
Added	1

🚀 Conventional commits found.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.37%. Comparing base (416dd46) to head (c13c2b4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #992   +/-   ##
=======================================
  Coverage   90.37%   90.37%           
=======================================
  Files         103      103           
  Lines        6958     6959    +1     
  Branches      986      986           
=======================================
+ Hits         6288     6289    +1     
  Misses        471      471           
  Partials      199      199           

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