replace remote function instance creation according to interfaces v5

Author: gregor-j

Diff for: index.md

@@ -31,6 +31,11 @@ or
 or   
 `composer require php-sap/saprfc-kralik`
 
+**ATTENTION**:   
+Starting with PHP 8 and `php-sap/interfaces` 5.0.0 the function instance is
+created using the factory method `SapRfc::create()`.
+Before that it was `new SapRfc()`.
+
 ```php
 <?php
 //Include the composer autoloader ...
@@ -48,7 +53,7 @@ use phpsap\saprfc\SapRfc;
  *
  * In this case the configuration array is defined manually.
  */
-$result = (new SapRfc(
+$result = SapRfc::create(
   'MY_COOL_SAP_REMOTE_FUNCTION',
   [
       'IV_DATE' => (new DateTime('2019-12-31'))
@@ -61,7 +66,7 @@ $result = (new SapRfc(
       ConfigTypeA::JSON_USER   => 'username',
       ConfigTypeA::JSON_PASSWD => 'password'
   ])
-))->invoke();
+)->invoke();
 //The output array contains a DateTime object.
 echo $result['OV_DATE']->format('Y-m-d') . PHP_EOL;
 ```

Diff for: saprfc-function.md

@@ -22,6 +22,11 @@ therefore be stored as JSON by using `json_encode` on the `SapRfc` instance.
 
 Let's start with an example.
 
+**ATTENTION**:   
+Starting with PHP 8 and `php-sap/interfaces` 5.0.0 the function instance is
+created using the factory method `SapRfc::create()`.
+Before that it was `new SapRfc()`.
+
 ```php
 <?php
 use phpsap\classes\Config\ConfigTypeA;
@@ -31,7 +36,7 @@ use phpsap\saprfc\SapRfc;
  * The imaginary SAP remote function requires a
  * date as input and will return a date as output.
  */
-$function = new SapRfc('MY_COOL_SAP_REMOTE_FUNCTION');
+$function = SapRfc::create('MY_COOL_SAP_REMOTE_FUNCTION');
 /**
  * The instance in `$function` has no way to establish a connection
  * because it lacks the necessary configuration. Let's add that