Update Commands.md: Adding codecept run -g failed

Page: https://codeception.com/docs/reference/Commands#Run

Author: ThomasLandauer

docs/reference/Commands.md

@@ -233,16 +233,16 @@ Executes tests.
 
 Usage:
 
-* `codecept run acceptance`: run all acceptance tests
-* `codecept run tests/acceptance/MyCest.php`: run only MyCest
-* `codecept run acceptance MyCest`: same as above
-* `codecept run acceptance MyCest:myTestInIt`: run one test from a Cest
-* `codecept run acceptance MyCest:myTestInIt#1`: run one example or data provider item by number
-* `codecept run acceptance MyCest:myTestInIt#1-3`: run a range of examples or data provider items
-* `codecept run acceptance MyCest:myTestInIt@name.*`: run data provider items with matching names
-* `codecept run acceptance checkout.feature`: run feature-file
-* `codecept run acceptance -g slow`: run tests from *slow* group
-* `codecept run unit,functional`: run only unit and functional suites
+* `codecept run Acceptance`: run all acceptance tests
+* `codecept run tests/Acceptance/MyCest.php`: run only MyCest
+* `codecept run Acceptance MyCest`: same as above
+* `codecept run Acceptance MyCest:myTestInIt`: run one test from a Cest
+* `codecept run Acceptance MyCest:myTestInIt#1`: run one example or data provider item by number
+* `codecept run Acceptance MyCest:myTestInIt#1-3`: run a range of examples or data provider items
+* `codecept run Acceptance MyCest:myTestInIt@name.*`: run data provider items with matching names
+* `codecept run Acceptance checkout.feature`: run feature-file
+* `codecept run Acceptance -g slow`: run tests from *slow* group
+* `codecept run Unit,Functional`: run only unit and functional suites
 
 Verbosity modes:
 
@@ -268,6 +268,10 @@ Run with specific extension
 * `codecept run --ext DotReporter` run with DotReporter printer
 * `codecept run --ext "My\Custom\Extension"` run with an extension loaded by class name
 
+Re-Run failed tests
+
+* `codecept run -g failed`
+
 Full reference:
 {% highlight yaml %}
 Arguments: