Checkin .clang-format and an example file for discussion (shader-slang#1373)

* Checkin .clang-format and an example file for discussion

* Update clang-format settings per discussion comments

* update .clang-format

* Move .clangformat file to extras/ folder

Co-authored-by: Yong He <yhe@nvidia.com>
Co-authored-by: Tim Foley <tfoleyNV@users.noreply.github.com>

Author: csyonghe

extras/.clang-format

@@ -0,0 +1,48 @@
+---
+BasedOnStyle: LLVM
+IndentWidth: 4
+---
+Language: Cpp
+# Force pointers to the type for C++.
+IndentPPDirectives: AfterHash
+DerivePointerAlignment: false
+PointerAlignment: Left
+BinPackArguments: false
+BinPackParameters: false
+ExperimentalAutoDetectBinPacking: false
+AllowAllParametersOfDeclarationOnNextLine: true
+NamespaceIndentation: None
+FixNamespaceComments: true
+AccessModifierOffset: -4
+AlignTrailingComments: false
+ConstructorInitializerIndentWidth: 4
+AlignEscapedNewlinesLeft: true
+PenaltyReturnTypeOnItsOwnLine: 100
+ColumnLimit: 100
+IncludeBlocks: Preserve
+AlignAfterOpenBracket: AlwaysBreak
+IndentCaseBlocks: true
+SortIncludes: true
+SortUsingDeclarations: true
+UseTab: Never
+BreakConstructorInitializers: BeforeComma
+BreakInheritanceList: BeforeComma
+BreakBeforeBraces: Custom
+BraceWrapping:
+  AfterCaseLabel: true
+  AfterClass: true
+  AfterEnum: true
+  AfterStruct: true
+  AfterUnion: true
+  SplitEmptyFunction: false
+  AfterControlStatement: Always
+  AfterFunction: true
+  AfterNamespace: true
+  AfterExternBlock: true
+  BeforeCatch: true
+  BeforeElse: true
+  # BeforeLambdaBody: true
+  # BeforeWhile: false
+  IndentBraces: false
+  SplitEmptyFunction: false
+  SplitEmptyRecord: false