Detect content type based on WARC-Resource-Type

[benoit74]

Fix #296

Nota: this PR is slightly enhanced compared to what has been proposed in the issue due to some stuff that has been realized during implementation

Changes:

• use WARC-Resource-Type header when available inside the WARC to decide what kind of content / rewrite we have
  • fallback to mimetype-only decision will most probably continue to exist since the WARC-Resource-Type is not guaranteed to be present inside the WARC, for old WARC but also for WARC created with other tools then Browsertrix crawler
• add a test case on the test website faking some content-type headers (warc2zim 2.0.0 is just failing on this test set)
• add corresponding WARC to the test dataset for automated testing, at least ensuring we can convert the WARC
• add temporary (to be removed once we are confident about the new logic) log when result from warc-resource-type + mimetype method is different from the mimetype-only method

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 76.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 84.01%. Comparing base (24aeafa) to head (92a456f).

Files	Patch %	Lines
src/warc2zim/content_rewriting/generic.py	76.00%	3 Missing and 3 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #306 +/- ## ========================================== - Coverage 84.17% 84.01% -0.17% ========================================== Files 14 14 Lines 1245 1270 +25 Branches 240 249 +9 ========================================== + Hits 1048 1067 +19 - Misses 152 155 +3 - Partials 45 48 +3 ```

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[benoit74]

Issues around code coverage are not new. They are now properly tracked in #307 and #308.