[Localization] Missing steps for generating and editing resx on Linux and Mac

We need to generate and edit in localization. However [the document](https://github.com/aspnet/Docs/blob/master/aspnetcore/fundamentals/localization.md#working-with-resource-files) describes the steps only on the Visual Studio on Windows. Now ASP.NET Core is cross platform so could you describe the supported steps on Linux and Mac OS.

At least, the document should describe the XML schema and the sample XML for resx.

Edit by @Rick-Anderson : See [LocalizationResourceGenerator](https://github.com/hishamco/LocalizationResourceGenerator) which generates & translates resources based on default `.resx`

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#### Document Details

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* ID: d1833676-ff1b-c587-cc9c-81afffa8ef68
* Version Independent ID: ad989395-3f49-4d55-521e-cf6fe56281ee
* Content: [Globalization and localization in ASP.NET Core](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/localization?view=aspnetcore-2.1#feedback)
* Content Source: [aspnetcore/fundamentals/localization.md](https://github.com/aspnet/AspNetCore.Docs/blob/master/aspnetcore/fundamentals/localization.md)
* Product: **aspnet-core**
* Technology: **aspnetcore-fundamentals**
* GitHub Login: @Rick-Anderson
* Microsoft Alias: **riande**