jna/plugins: added readme
> - infos/version = 1
> - exports/has/set = 1
> - exports/has/get = 1
+
+# Sorted checker plugin
+
+This plugin checks if an elektra array is sorted.
+
+To activate the plugin add the following meta-key (with empty value) to an existing array:
+
+``check/sorted = ``
+
+The plugin will then assume the array elements are primitive types (e.g. string or integer) and will check if they are sorted in ascending order.
+If the array elements are not primitive types and have sub-keys, it is possible to provide a name to this sub-key.
+E.g. to sort by a sub-key `/nr`:
+
+``check/sorted = nr``
+
+It is also possible to change the sorting direction by setting the key `check/sorted/direction` to either *asc* or *desc*.
+
+## Metakey summary
+
+| Metakey | Description |
+|------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| check/sorted | Activates the plugin. 2 possible values: <br/> - Empty: uses values of array elements directly <br/> - String representing a sub-key: uses value of sub-key for sorting |
+| check/sorted/direction | Optional.<br/> Possible values:<br/> - *asc*: Ascending order (default, if direction is omitted)<br/>- *desc*: Descending order |
