static getParentLocaleTag(sSrcFolder, sCLDRTag) {
		const sFileName = join(sSrcFolder, "cldr-core", "supplemental", "parentLocales.json");

		return fileContent.getContent(sFileName).supplemental.parentLocales.parentLocale[sCLDRTag];
	}
Returns the parent locale tag for a given CLDR tag if one is mentioned in the supplemental.json of the downloaded
CLDR data.

@param {string} sSrcFolder
  The source folder for the CLDR data
@param {string} sCLDRTag
  The language tag as defined by the IETF BCP 47, e.g. "en", "de-CH" or "sr-Latn"
@returns {string|undefined}
  The CLDR tag of the parent locale for the given CLDR tag or <code>undefined</code> if no parent locale is
  defined