Implemented a very inefficient solution for lattice paths count

- Only runs up until 10 grid size. Runs in ~1m
- On a grid size of 11, it already results in
  `FATAL ERROR: JS Allocation failed - process out of memory`
  and runs up to 4m
Turn to math!

- Found an explanation about using combinatorics
  to calculate permutations. So did not come up
  with this solution but definitely learned something
  new :)