add documentation

docs/configuration.md

@@ -196,6 +196,7 @@ Variables that are marked as being templated are capable of using mockery-provid
 
 | name                    | description                                                                                                                                                                                                                                                                                   |
 |-------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| ConfigDir               | The directory path of the config file used. This is used to allow generation of mocks in a directory relative to the `.mockery.yaml` file, e.g. external interfaces.                                                                                                                          |
 | InterfaceDir            | The directory path of the original interface being mocked. This can be used as <br>`#!yaml dir: "{{.InterfaceDir}}"` to place your mocks adjacent to the original interface. This should not be used for external interfaces.                                                                 |
 | InterfaceDirRelative    | The directory path of the original interface being mocked, relative to the current working directory. If the path cannot be made relative to the current working directory, this variable will be set equal to `PackagePath`                                                                  |
 | InterfaceFile           | The file path of the original interface being mocked. **NOTE:** This option will only write one mock implementation to the output file. If multiple mocks are defined in your original file, only one mock will be written to the output.                                                     |