Initial yt-dlp implementation (#3)

* Added basic runner for yt-dlp commands

* Updated formatting rules

* Added JSON runner; Added test script for CLI interactions

* Reworked yt-dlp runner; added proper test mocks

lib/utils/string_utils.ex

@@ -0,0 +1,14 @@
+defmodule Pinchflat.Utils.StringUtils do
+  @moduledoc """
+  Utility functions for working with strings
+  """
+
+  @doc """
+  Converts a string to kebab-case (ie: `hello world` -> `hello-world`)
+  """
+  def to_kebab_case(string) do
+    string
+    |> String.replace(~r/[\s_]/, "-")
+    |> String.downcase()
+  end
+end