Fix logic of rewrite mode computation for cases raised in #326

[benoit74]

Fix #326

[benoit74]

Nota: I checked also few other task I had in mind and which have completed since 2.0.1 release to confirm there are no other known cases for now: https://farm.openzim.org/recipes/100rabbits, https://farm.openzim.org/recipes/website.test.openzim.org_en_all, https://farm.openzim.org/recipes/cloudflare.com_en_learning-center)

[rgaudin]

LGTM but I cannot judge the strategy here.
I think we should have a comment in the code explaining the strategy: why are we not simply relying on mimetype, etc

[benoit74]

Thank you a lot for the remark, I've indeed added documentation (in technical_architecture.md) and opened a discussion with webrecorder to see if we can enhance the situation (things have changed a bit since the original discussions about the WARC-Resource-Type header): webrecorder/browsertrix-crawler#630