Added Solution 4 Journey to the Moon Graph Theory

[BhanukaUOM]

No description provided.

[Kvaibhav01]

Here are the few things to consider when you make a new PR for this problem:

1. Make sure you read the rules listed here. Especially, number 2.
2. The code you provided is completely different from the skeleton code provided by HackerRank, try to use that code by completing the journeyToMoon function as they say.
   Else, explain your code with comments in between.