feat: add dynamic file structures in loop using yield-tag

[kj-9]

What I did:

• Added a new Jinja extension in copier/jinja_ext.py to handle yield tags
  • This is a lightweight extension that detects yield tags and sets up the necessary context through jinja_env
• Updated _render_path to return multiple destination paths and their corresponding contexts when yield tags are present
  • Internally, delegated the recursive logic for generating paths and contexts from yield tags to the _render_parts function
• Added extra_context parameter to _render_file to enable injection of contexts generated from yield tags

[kj-9]

hopefully closes #1271

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.73%. Comparing base (8391966) to head (7164aa7).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1855      +/-   ##
==========================================
+ Coverage   97.67%   97.73%   +0.06%     
==========================================
  Files          49       51       +2     
  Lines        5238     5349     +111     
==========================================
+ Hits         5116     5228     +112     
+ Misses        122      121       -1     

Flag	Coverage Δ
unittests	97.73% <100.00%> (+0.06%)	⬆️

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