fix(decode): use invariant culture for decimal strings

[ThisFunctionalTom]

Summary

This fixes decimal decoding from JSON strings when the current process culture uses a comma decimal separator.

Decode.decimal was using the current culture for string parsing, which meant values like "0.7833" could fail under cultures such as de-DE even though JSON numbers use . as the decimal separator.

Changes

• parse decimal strings with CultureInfo.InvariantCulture
• apply the fix in both Thoth.Json and Thoth.Json.Core
• add a regression test that switches the current culture to de-DE and verifies "0.7833" still decodes successfully

Validation

• .\\build.bat test newtonsoft
• .\\build.bat test system-text-json

[njlr]

Is there a test case with a negative number?
Not every culture & number style accepts - IIRC

[ThisFunctionalTom]

Is there a test case with a negative number? Not every culture & number style accepts - IIRC

Didn't know that :-).

Have changed the test to use negative number and bigger then 1000 for the 1000 separator and test it with different cultures.

[ThisFunctionalTom]

One question. I just read the documenation of the easybuild.commitlinter and easybuild.changeloggen.

Should I squash the two commits and force-push so that the changelog is clean?