Add localization support

[filzrev]

When generating document from OpenCLI spec file.
Multilingual support (i18n) is required for some fields (summary, description, examples).

So I though it need standard rules to support localization for OpenCLI spec.

Example

1. Localization is defined by using XLIFF file format.
2. Localization files are placed under xlf directory (Example of .NET CLI https://github.com/dotnet/sdk/tree/main/src/Cli/dotnet/xlf)
3. Localization target id of <trans-unit> use JsonPath representation of target field.
   (e.g. $.options[?(@.name == '--help')].description)

Note

JsonPath is used to specify element based on other field.
When using JsonPointer. It need specify fields by array index instead of name field.
And I though it's redundant to define unique id per field on OpenCLI spec side.