Add clang-format style file and script

.clang-format

@@ -0,0 +1,12 @@
+---
+BasedOnStyle: LLVM
+AllowShortBlocksOnASingleLine: 'true'
+AllowShortCaseLabelsOnASingleLine: 'true'
+AllowShortFunctionsOnASingleLine: Inline
+AllowShortIfStatementsOnASingleLine: WithoutElse
+AllowShortLambdasOnASingleLine: Inline
+AllowShortLoopsOnASingleLine: 'false'
+AlwaysBreakBeforeMultilineStrings: 'true'
+IndentWidth: '4'
+
+...

main.cpp

@@ -1,7 +1,7 @@
 #include <iostream>
 
 int main() {
-	std::cout << "Hello World!" << std::endl;
+    std::cout << "Hello World!" << std::endl;
-    
+
     return 0;
 }

tools/format.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+if [[ "$OSTYPE" == "darwin"* ]]; then
+  clang_format_command="clang-format"
+  clang_tidy_command="run-clang-tidy"
+fi
+if [[ "$OSTYPE" == "linux"* ]]; then
+  clang_format_command="clang-format-11"
+  clang_tidy_command="run-clang-tidy-11"
+fi
+
+eval "$clang_format_command -i *.h *.cpp -style=file"
+eval "$clang_tidy_command -fix"