support bazel complie this project and format code.

learn_class/modern_cpp_30/RAII/stack.cpp

@@ -0,0 +1,23 @@
+//
+// Created by light on 19-12-9.
+//
+#include <iostream>
+class Obj {
+public:
+  Obj() { puts("Obj()"); }
+  ~Obj() { puts("~Obj()"); }
+};
+void foo(int n) {
+  Obj obj;
+  if (n == 42)
+    throw "life, the universe and everything";
+}
+// 不管是否发生了异常，obj 的析构函数都会得到执行。
+int main() {
+  try {
+    foo(41);
+    foo(42);
+  } catch (const char *s) {
+    puts(s);
+  }
+}