Add time module with to_duration_string

Which turn a float into a `mm:ss` string

src/musicplayer/time/time.gleam

@@ -0,0 +1,23 @@
+import gleam/float
+import gleam/int
+import gleam/string
+
+pub fn to_duration_string(seconds: Float) -> String {
+  let total =
+    seconds
+    |> float.max(0.0)
+    |> float.truncate
+
+  let minutes = total / 60
+  let seconds = total % 60
+
+  let mins =
+    int.to_string(minutes)
+    |> string.pad_start(to: 2, with: "0")
+
+  let secs =
+    int.to_string(seconds)
+    |> string.pad_start(to: 2, with: "0")
+
+  mins <> ":" <> secs
+}

test/musicplayer/time/time_test.gleam

@@ -0,0 +1,32 @@
+import gleam/list
+import gleeunit
+
+import musicplayer/time/time
+
+pub fn main() -> Nil {
+  gleeunit.main()
+}
+
+type TestCase {
+  TestCase(seconds: Float, expected: String)
+}
+
+pub fn to_duration_string_test() {
+  let test_cases = [
+    TestCase(-1.0, "00:00"),
+    TestCase(0.0, "00:00"),
+    TestCase(9.0, "00:09"),
+    TestCase(10.0, "00:10"),
+    TestCase(11.0, "00:11"),
+    TestCase(60.0, "01:00"),
+    TestCase(61.0, "01:01"),
+    TestCase(120.0, "02:00"),
+    TestCase(600.0, "10:00"),
+    TestCase(6000.0, "100:00"),
+    TestCase(6001.0, "100:01"),
+  ]
+
+  list.each(test_cases, fn(tc) {
+    assert tc.expected == time.to_duration_string(tc.seconds)
+  })
+}