Hands on: Complete tests and implement a working solution for `local_maxima`

[pberkes]

Write a working implementation of the local_maxima function from slide 5:

1. The module test_local_maxima [1] contains tests corresponding to the examples on slide 6. Complete the last test with the last example in slide 6.

2. Write the implementation of the local_maxima function in the module local_maxima [2], running the tests as you go until you have code that makes all tests pass.

3. Clean up the code until you are happy, making sure that the tests still pass

[1] https://github.com/ASPP/2022-bilbao-testing-debugging/tree/master/hands_on/local_maxima/test_local_maxima.py
[2] https://github.com/ASPP/2022-bilbao-testing-debugging/blob/master/hands_on/local_maxima/local_maxima.py