(20) New exercise | Tower of Hanoi

Because

I think this exercise should be the last one because in my mind it's the most difficult one.

Related to #27265

[x] I have thoroughly read and understand The Odin Project Contributing Guide
[x] The title of this PR follows the location of change: brief description of change format, e.g. 01_helloWorld: Update test cases
[x] The Because section summarizes the reason for this PR
[x] The This PR section has a bullet point list describing the changes in this PR
[x] If this PR addresses an open issue, it is linked in the Issue section
[x] If this PR includes any changes that affect the solution of an exercise, I've also updated the solution in the /solutions folder