Add Backtracking

[AnshumanM6]

Backtracking is not present. Backtracking is an algorithmic-technique for solving problems recursively by trying to build a solution incrementally.

[sragha45]

Assign this to me! I can do this :)

[ghost]

I can implement backtracing in problems like printing all permutations in a given string etccc Assign this to me...

[Shakileash5]

@AnshumanM6 im working on in ,I will add it

[palak199]

I have already worked on problems like sudoku with backtracking so I can implement this. for reference you can refer to my github repo also. kindly assign it to me

[Aliex-dev]

i can implement backtracking

[Aliex-dev]

i have made a pr please do review