Update to mdbook 0.5

[ehuss]

This is a preliminary PR for updating mdbook-i18n-helpers to mdbook 0.5. This should wait until at least mdbook 0.5 is released.

I haven't had a chance to do much testing, but the basics seem to work.

There is a migration guide that explains all the changes in the release.

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[qwandor]

Please update the relevant changelogs too.

[codecov-commenter]

Codecov Report

:x: Patch coverage is 18.51852% with 22 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 85.53%. Comparing base (886f15e) to head (191312f). :warning: Report is 35 commits behind head on main.

Files with missing lines	Patch %	Lines
i18n-helpers/src/preprocessors/gettext.rs	0.00%	7 Missing :warning:
fuzz/src/lib.rs	0.00%	6 Missing :warning:
i18n-helpers/src/bin/mdbook-gettext.rs	0.00%	4 Missing :warning:
i18n-helpers/src/xgettext.rs	71.42%	0 Missing and 2 partials :warning:
mdbook-tera-backend/src/main.rs	0.00%	2 Missing :warning:
mdbook-tera-backend/src/tera_renderer/renderer.rs	0.00%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #284      +/-   ##
==========================================
+ Coverage   84.74%   85.53%   +0.78%     
==========================================
  Files          15       17       +2     
  Lines        3377     3339      -38     
  Branches     3377     3339      -38     
==========================================
- Hits         2862     2856       -6     
+ Misses        413      381      -32     
  Partials      102      102              

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[qwandor]

This looks reasonable and the tests pass, have you had a chance to do much manual testing?

[ehuss]

I have not done significant testing. I mainly verified that a local copy of comprehensive-rust and rust-by-example worked with the mdbook-gettext preprocessor. The different languages seemed to appear as I expected. I also verified that mdbook-xgettext was able to extract the po files, but I didn't go beyond that.

If you have suggestions for more things for me to try, I'd be happy to do that. I wasn't really sure what to try.