docs(test-helpers) Add retry page

Author: tony

docs/test-helpers/index.md

@@ -8,6 +8,7 @@ Test helpers for libtmux and downstream libraries.
 constants
 environment
 random
+retry
 temporary
 waiter
 ```

docs/test-helpers/retry.md

@@ -0,0 +1,15 @@
+(retry)=
+
+# Retry Utilities
+
+Retry helper functions for libtmux test utilities. These utilities help manage testing operations that may require multiple attempts before succeeding.
+
+## Basic Retry Functionality
+
+```{eval-rst}
+.. automodule:: libtmux.test.retry
+   :members:
+   :undoc-members:
+   :show-inheritance:
+   :member-order: bysource
+```