clang-format indents case labels with in switches matching existing XNNPACK style.

PiperOrigin-RevId: 421054265
diff --git a/.clang-format b/.clang-format
index e651c3d..486bda4 100644
--- a/.clang-format
+++ b/.clang-format
@@ -9,6 +9,7 @@
 PointerAlignment: Left
 ForEachMacros: ['XNN_UNPREDICTABLE', 'XNN_LIKELY', 'XNN_UNLIKELY']
 IfMacros: ['IF']
+IndentCaseLabels: true
 SpaceBeforeParens: Custom
 SpaceBeforeParensOptions:
   AfterControlStatements: true