feature: Added the ability to localize RJSF internal strings

[heath-freenome]

Reasons for making this change

True fix for #205 to support localizing the internal strings in @rjsf

• In @rjsf/utils, added TranslatableString enum and englishStringTranslator() and replaceStringParameters() to support localization
  • Also updated the Registry type to add the translateString function
  • Added 100% unit testing for the new functions
• In @rjsf/core, added a new translateString prop to FormProps as well as using that prop in the registry if provided
  • Updated the getDefaultRegistry() to set translateString to englishStringTranslator
  • Updated ArrayField, BooleanField, MultiSchemaField, ObjectField, SchemaField, AddButton, IconButtons, ErrorList, WrapIfAdditionalTemplate and AltDateWidget and FileWidget to use translateString
  • Added the markdown-to-jsx to support localizing the UnsupportedField
• In all the themes, updated ErrorList, IconButtons, AddButton, WrapIfAdditionalTemplate and where applicable AltDateWidget to use translateString from the registry
  • Updated the snapshots for UnsupportedField based on the cleaned up translation formatting
• In @rjsf/semantic-ui, updated the FieldErrorTemplate and FieldHelpTemplate to use the errorId() and helpId() functions
• Updated the utility-functions docs for the enums and the new functions
• Updated the form-props docs to describe the new translateString prop
• Updated the CHANGELOG accordingly

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests. I've run npm run test:update to update snapshots, if needed.
  • I've updated docs if needed
  • I've updated the changelog with a description of the PR
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[nickgros]

Looks great! Couple of notes--not sure if they are real issues. See comments before merging.

[zlldnv]

Hey @heath-freenome thank you very much for adding this improvement into library!
Would more examples how to use this improvement arrive? Even here or in the docs?
Is ‘t’ from i18next a good candidate for the translationString prop? If yes how to use it with json schema?
Thanx!

[heath-freenome]

@zlldnv Have you looked at the examples in the docs? All of the translatable strings can be found here. I'm not familiar with t.