Update documentation for new config options

README.md

@@ -151,19 +151,23 @@ commands = ...
 > the child environment with a different value.
 
 Alternatively, we can skip specifying all of our dependencies for a test environment in
-the Tox config and just install all of our Poetry dev-dependencies automatically:
+the Tox config and install Poetry dependency groups directly:
 
 ```ini
 [testenv]
 description = Some very cool tests
 require_locked_deps = true
-install_dev_deps = true
+poetry_dep_groups =
+    dev
 commands = ...
 ```
 
-> **Note:** Setting `install_dev_deps = true` on an environment that also installs the
+> **Note:** Setting `poetry_dep_groups = [dev]` on an environment that also installs the
 > project package is functionally equivalent to running `poetry install`.
 
+> **Note:** The `install_dev_deps` configuration option is deprecated. See \[Configuration
+> Options\](#configuration-options\] for more information.
+
 Finally, we can also install an unlocked dependency (a dependency which doesn't take its
 version from the Poetry lockfile) into the test environment alongside the locked ones. We
 need to remove the `require_locked_deps = true` option, otherwise the environment will