Extract mpv/key to input

To separate the concern from `mpv`

test/input/input_test.gleam

@@ -0,0 +1,29 @@
+import gleam/list
+import gleeunit
+
+import input/key.{type Key, Char, csi, esc}
+
+pub fn main() -> Nil {
+  gleeunit.main()
+}
+
+type TestCase {
+  TestCase(input: List(String), expected: Key)
+}
+
+pub fn key_from_list_test() {
+  let test_cases = [
+    TestCase(["c"], Char("c")),
+    TestCase([esc, csi, "D"], key.Left),
+    TestCase([esc, csi, "C"], key.Right),
+    TestCase([esc, csi, "A"], key.Up),
+    TestCase([esc, csi, "B"], key.Down),
+    TestCase([esc, csi], key.Continue),
+    TestCase([esc], key.Continue),
+    TestCase([], key.Continue),
+  ]
+
+  list.each(test_cases, fn(tc) {
+    assert tc.expected == key.from_list(tc.input)
+  })
+}