Add initial support for localization

[orhoj]

Purpose

Add localization for verifiable credentials.

Changes

• Fetch the localization files and apply them when displaying a verifiable credential.

It is missing some validation when getting the localization file, where we want to ensure that all the keys from the schema are present. We will do that soonTM.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.