(#25) Add a Django sample app

[imranariffin]

• Create sample celery task usage
• Include compare celery vs aiotaskq sample code in tests
• Add ref to sample code in README, add sample code README
• Include populate_db step in the tests

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 93.87097% with 19 lines in your changes missing coverage. Please review.

Project coverage is 98.22%. Comparing base (f02f6ce) to head (e6805e2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/aiotaskq/utils.py	70.58%	5 Missing ⚠️
...s/apps/sample_app_django/sample_app_django/asgi.py	0.00%	4 Missing ⚠️
...s/apps/sample_app_django/sample_app_django/wsgi.py	0.00%	4 Missing ⚠️
..._app_django/api/management/commands/populate_db.py	95.16%	3 Missing ⚠️
src/tests/apps/sample_app_django/manage.py	83.33%	2 Missing ⚠️
src/aiotaskq/app.py	95.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #68      +/-   ##
==========================================
- Coverage   99.21%   98.22%   -0.99%     
==========================================
  Files          18       38      +20     
  Lines         635     1298     +663     
==========================================
+ Hits          630     1275     +645     
- Misses          5       23      +18     

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