Update release notes based on new CSV metadata files. (#2782)

release_notes.txt

@@ -10,6 +10,14 @@ Metadata changes:
    44 (en), 98 (en, fa), 212 (en), 380 (en, uk), 385 (en), 420 (en),
    852 (en, zh)
  - Updated / refreshed time zone meta data.
+New Metadata files:
+ - The phone and short number metadata of all regions are available now in
+   CSV format, at resources/metdata directory. This helps in better
+   readability and maintainance compared to RegEx representation for all
+   numbering metadata. The legacy XML metadata files (like
+   PhoneNumberMetadata.xml) are now auto genarated from this data; so now
+   users can also build tools around CSV representation based on their
+   needs/requirements.
 
 May 25, 2022: v8.12.49
 Metadata changes: