feat: Added loop filter.

filters_test.nu

@@ -0,0 +1,25 @@
+#!/usr/bin/env nu
+
+use std [assert];
+
+use ./filters.nu [complex-filter loop "parse filter"];
+
+#[test]
+def loop_has_defaults [] {
+  let got = (loop 10 1);
+  let want = (complex-filter 'loop' { loop: 10 size: 1 });
+  assert equal $got $want;
+}
+
+#[test]
+def setting_time_sets_start_to-1 [] {
+  let got = (loop 10 1 -t 0.5);
+  let want = (complex-filter 'loop' {
+      loop: 10
+      size: 1
+      start: -1
+      time: 0.5
+    });
+
+  assert equal $got $want;
+}