Added isKey and getType methods to the documentation (#9111)

docs/en/api/preferences.rst

@@ -177,6 +177,45 @@ Arduino-esp32 Preferences API
 
  **Note** 
  * A message providing the reason for a failed call is sent to the arduino-esp32 ``log_e`` facility.
+
+
+``isKey``
+*************
+
+ Check if a key-value pair from the currently open namespace exists.
+
+ .. code-block:: arduino
+ 
+ bool isKey(const char * key)
+ ..
+
+ **Parameters**
+ * ``key`` (Required)
+ - the name of the key to be checked. 
+
+ **Returns**
+ * ``true`` if key-value pair exists; ``false`` otherwise.
+
+ **Note** 
+ * Attempting to check a key without a namespace being open will return false.
+
+
+``getType``
+*************
+
+ Returns the type of a key-value pair from the currently open namespace.
+
+ .. code-block:: arduino
+ 
+ PreferenceType getType(const char * key)
+ ..
+
+ **Parameters**
+ * ``key`` (Required)
+ - the name of the key to be checked. 
+
+ **Returns**
+ * PreferenceType element contaning the type of the key-value pair or PT_INVALID on error.
 
 
 ``putChar, putUChar``