Add code for checking balanced tree in C++

[MuditWadhwa]

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Hi, I am good in DSA but a beginner in open source. Could you please allow me to work on this issue and contribute well commented code for checking balanced tree in C++ and add the label hacktoberfest-accepted as well?

[avinash201199]

Go ahead :) @MuditWadhwa
will add the tag hacktoberfest-accepted on pr