doc: add hasIntl to test/common/README.md

Commit d7e4ae1
("test: add common.hasIntl") added common.hasIntl but I was not able to
find it in the README.md so this commit adds it.

PR-URL: #13699
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/common/README.md

@@ -106,6 +106,11 @@ Checks for 'openssl'.
 
 Checks `hasCrypto` and `crypto` with fips.
 
+### hasIntl
+* return [<Boolean>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type)
+
+Checks if [internationalization] is supported.
+
 ### hasIPv6
 * return [<Boolean>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type)
 
@@ -322,3 +327,4 @@ implementation with tests from
 [W3C Web Platform Tests](https://github.com/w3c/web-platform-tests).
 
 [MDN-Function]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Normal_objects_and_functions
+[internationalization]: https://github.com/nodejs/node/wiki/Intl