clang-tidy: Add modernize-use-nullptr

Adding the modernize-use-nullptr check in clang-tidy provides several
benefits like
 - Consistency with Modern C++ Standards
 - Reduced Ambiguity
 - Improved Code Safety

Change-Id: I9938fd024215338d87eec313e86111844c2dd91a
Signed-off-by: Jayanth Othayoth <ojayanth@gmail.com>
diff --git a/style/cpp/.clang-tidy b/style/cpp/.clang-tidy
index 957d09a..31cac99 100644
--- a/style/cpp/.clang-tidy
+++ b/style/cpp/.clang-tidy
@@ -1,6 +1,7 @@
 Checks: '
     -*,
     bugprone-unchecked-optional-access,
+    modernize-use-nullptr,
     readability-function-size,
     readability-function-cognitive-complexity
 '