feat: Add xml and lxml tree serializers

[tefra]

📒 Description

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Resolves #849

🔗 What I've Done

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💬 Comments

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🛫 Checklist

• Updated docs
• Added unit-tests
• Sample tests pass
• W3C tests pass

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.97%. Comparing base (9da8d63) to head (d0e2d56).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #975   +/-   ##
=======================================
  Coverage   99.97%   99.97%           
=======================================
  Files         112      115    +3     
  Lines        8978     9040   +62     
  Branches     2138     2149   +11     
=======================================
+ Hits         8976     9038   +62     
  Misses          1        1           
  Partials        1        1           

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud