[Intl] Add link refs for classes

Add links for all classes to easily check code source.

Author: mohamedGasmii

components/intl.rst

@@ -166,7 +166,7 @@ to catching the exception, you can also check if a given script code is valid::
 Country Names
 ~~~~~~~~~~~~~
 
-The ``Countries`` class provides access to the name of all countries according
+The :class:`Symfony\\Component\\Intl\\Countries` class provides access to the name of all countries according
 to the `ISO 3166-1 alpha-2`_ list and the `ISO 3166-1 alpha-3`_ list
 of officially recognized countries and territories::
 
@@ -233,7 +233,7 @@ Locales
 A locale is the combination of a language, a region and some parameters that
 define the interface preferences of the user. For example, "Chinese" is the
 language and ``zh_Hans_MO`` is the locale for "Chinese" (language) + "Simplified"
-(script) + "Macau SAR China" (region). The ``Locales`` class provides access to
+(script) + "Macau SAR China" (region). The :class:`Symfony\\Component\\Intl\\Locales` class provides access to
 the name of all locales::
 
     use Symfony\Component\Intl\Locales;
@@ -269,7 +269,7 @@ to catching the exception, you can also check if a given locale code is valid::
 Currencies
 ~~~~~~~~~~
 
-The ``Currencies`` class provides access to the name of all currencies as well
+The :class:`Symfony\\Component\\Intl\\Currencies` class provides access to the name of all currencies as well
 as some of their information (symbol, fraction digits, etc.)::
 
     use Symfony\Component\Intl\Currencies;
@@ -317,7 +317,7 @@ to catching the exception, you can also check if a given currency code is valid:
 Timezones
 ~~~~~~~~~
 
-The ``Timezones`` class provides several utilities related to timezones. First,
+The :class:`Symfony\\Component\\Intl\\Timezones` class provides several utilities related to timezones. First,
 you can get the name and values of all timezones in all languages::
 
     use Symfony\Component\Intl\Timezones;