fix(config): do not raise error for bad date_from_meta.default_time value and fallback to default

[Guts]

Closes #290

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 80.45%. Comparing base (09e4ce4) to head (38c477f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #300      +/-   ##
==========================================
- Coverage   80.65%   80.45%   -0.20%     
==========================================
  Files           9        9              
  Lines         615      614       -1     
  Branches      128      128              
==========================================
- Hits          496      494       -2     
- Misses         82       83       +1     
  Partials       37       37              

Flag	Coverage Δ
unittests	80.45% <25.00%> (-0.20%)	⬇️

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Files	Coverage Δ
mkdocs_rss_plugin/config.py	100.00% <100.00%> (ø)
mkdocs_rss_plugin/plugin.py	89.92% <0.00%> (-0.78%)	⬇️