Add clang-format file

Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.

Kernel/FileSystem/SyntheticFileSystem.h

@@ -1,9 +1,9 @@
 #pragma once
 
+#include <AK/HashMap.h>
 #include <Kernel/FileSystem/FileSystem.h>
 #include <Kernel/FileSystem/Inode.h>
 #include <Kernel/UnixTypes.h>
-#include <AK/HashMap.h>
 
 class SynthFSInode;
 
@@ -47,6 +47,7 @@ struct SynthFSInodeCustomData {
 class SynthFSInode final : public Inode {
     friend class SynthFS;
     friend class DevPtsFS;
+
 public:
     virtual ~SynthFSInode() override;