8305206: Add @spec tags in java.base/java.* (part 1)

Reviewed-by: alanb, naoto, darcy, lancea, dfuchs, iris, mchung

src/java.base/share/classes/java/text/NumberFormat.java

@@ -586,6 +586,8 @@ public abstract class NumberFormat extends Format  {
      *
      * @param inLocale the desired locale
      * @return the {@code NumberFormat} instance for currency formatting
+     *
+     * @spec https://www.unicode.org/reports/tr35 Unicode Locale Data Markup Language (LDML)
      */
     public static NumberFormat getCurrencyInstance(Locale inLocale) {
         return getInstance(inLocale, null, CURRENCYSTYLE);