clang-tidy: Enable readability-string-compare check

This check finds string comparisons using the compare method.
A common mistake is to use the string’s compare method instead of
using the equality or inequality operators.

Change-Id: I261afa51d6af1db5afb94a127f45df7544911af9
Signed-off-by: Pavithra Barithaya <pavithrabarithaya07@gmail.com>
diff --git a/.clang-tidy b/.clang-tidy
index 9ece14b..3856aa5 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -247,6 +247,7 @@
 readability-redundant-preprocessor,
 readability-simplify-subscript-expr,
 readability-static-definition-in-anonymous-namespace,
+readability-string-compare,
 readability-suspicious-call-argument,
 readability-uniqueptr-delete-release,
 readability-uppercase-literal-suffix'