input: Write a python function to filter strings that start with a given letter.
  assert get_strings_with_prefix(["apple", "banana", "kiwi", "melon"], "a") == ["apple"]
  assert get_strings_with_prefix(["apple", "banana", "kiwi", "melon"], "b") == ["banana"]
  assert get_strings_with_prefix(["apple", "banana", "kiwi", "melon"], "m") == ["melon"]
  assert get_strings_with_prefix(["apple", "banana", "kiwi", "melon"], "k") == ["kiwi"]
  assert get_strings_with_prefix(["apple", "banana", "kiwi", "melon"], "z") == []
output: def get_strings_with_prefix(strings, prefix):
      return [s for s in strings if s.startswith(prefix)]