capitalizing C++

Author: the1scient

README.md

@@ -99,7 +99,7 @@ make sure its build process is working correctly by running `yarn run rebuild-no
 If you are on macOS, this typically is related to Xcode issues (like not having agreed
 to the Terms of Service by running `sudo xcodebuild` after a fresh Xcode installation).
 
-##### Error with `c++` on macOS when running `yarn`
+##### Error with `C++` on macOS when running `yarn`
 
 If you are getting compiler errors when running `yarn` add the environment variable `export CXX=clang++`