Prepare 8.21.1 release

Signed-off-by: Mior Muhammad Zaki <crynobone@gmail.com>

CHANGELOG-8.x.md

@@ -1,7 +1,19 @@
-# Change for 8.x
+# Changes for 8.x
 
 This changelog references the relevant changes (bug and security fixes) done to `orchestra/testbench-core`.
 
+## 8.21.1
+
+Released: 2024-01-22
+
+### Changes
+
+* Support nested configuration files.
+
+### Fixes
+
+* Fixes issue with Livewire testing where calling `$router->getRoutes()->refreshActionLookups()` caused tests to fail.
+
 ## 8.21.0
 
 Released: 2024-01-19