Added the missing "experimental" notices in some components

Author: javiereguiluz

components/http_client.rst

@@ -11,7 +11,8 @@ The HttpClient Component
 
 .. versionadded:: 4.3
 
-    The HttpClient component was introduced in Symfony 4.3.
+    The HttpClient component was introduced in Symfony 4.3 and it's still
+    considered an :doc:`experimental feature </contributing/code/experimental>`.
 
 Installation
 ------------

components/mailer.rst

@@ -7,6 +7,11 @@ The Mailer Component
 
     The Mailer component helps sending emails.
 
+.. versionadded:: 4.3
+
+    The Mailer component was introduced in Symfony 4.3 and it's still
+    considered an :doc:`experimental feature </contributing/code/experimental>`.
+
 Installation
 ------------
 

components/mime.rst

@@ -6,9 +6,14 @@
 The Mime Component
 ==================
 
-    The MIME component allows manipulating the MIME messages used to send emails
+    The Mime component allows manipulating the MIME messages used to send emails
     and provides utilities related to MIME types.
 
+.. versionadded:: 4.3
+
+    The Mime component was introduced in Symfony 4.3 and it's still
+    considered an :doc:`experimental feature </contributing/code/experimental>`.
+
 Installation
 ------------