Include dictionary video URLs in mapping.json files

[mdsrqbl]

1. Dictionary URLs should be moved to the mapping.json files, right beside the sign labels. This will place all the relevant information at a single place.
2. Add a script to validate those URLs as well.
3. add illustrations or corresponding images of the signs as well. e.g. associate a picture of apple with the sign of an apple. store these images somewhere public so others can use those as well.
4. Add version to the archived assets / release files.

Example:

{
  "components": ["pk-hfad-1_airplane", "pk-hfad-1_جگہ"],
  "label": "pk-hfad-1_airport",

  "reference-video-url": "https://github.com/sign-language-translator/sign-language-datasets/releases/download/v0.0.2/pk-hfad-1_airport.mp4",
  "illustration-url": "https://github.com/sign-language-translator/sign-language-datasets/releases/download/v0.0.5/airport.jpg"

  "token": {
    "en": ["airport", "airfield"],
    "ur": ["ہوائی اڈہ", "ہوائی اڈے", "ایئرپورٹ", "ایرپورٹ", "ائیرپورٹ"]
  }
}