Support generation of resx-comments

[earloc]

As a developer, I want the code-first-generator to also populate comments in a resx-file, to give more context of the intended usage of individual translatables to potential translators.

[earloc]

XML-comments [remarks] (https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/xmldoc/recommended-tags#remarks) seem to be the natural choice for this.

See #274