[clang] [clang-format] Add KwBreakBeforeCaseLabel (PR #227668)

[Björn Schäpers via cfe-commits]

================
@@ -281,6 +281,14 @@ class LineJoiner {
         return MergedLines;
     }
 
+    // Handle case labels preceded by a break statement
----------------
HazardyKnusperkeks wrote:

```suggestion
    // Handle case labels preceded by a break statement.
```
Comments end in full stop.

https://github.com/llvm/llvm-project/pull/227668