[clang] clang-format: Add IncludeSortKey option (PR #137840)

[Björn Schäpers via cfe-commits]

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@@ -4382,8 +4382,18 @@ struct FormatStyle {
     ///    #include "B/a.h"           #include "a/b.h"
     /// \endcode
     bool IgnoreCase;
+    /// When sorting includes in each block, Only take file extensions into
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HazardyKnusperkeks wrote:

```suggestion
    /// When sorting includes in each block, only take file extensions into
```

https://github.com/llvm/llvm-project/pull/137840