Move 'compareId' to comparators utils

app/soapbox/utils/comparators.ts

@@ -0,0 +1,23 @@
+'use strict';
+
+/**
+ * Compare numerical primary keys represented as strings.
+ * For example, '10' (as a string) is considered less than '9'
+ * when sorted alphabetically. So compare string length first.
+ *
+ * - `0`: id1 == id2
+ * - `1`: id1 > id2
+ * - `-1`: id1 < id2
+ */
+function compareId(id1: string, id2: string) {
+  if (id1 === id2) {
+    return 0;
+  }
+  if (id1.length === id2.length) {
+    return id1 > id2 ? 1 : -1;
+  } else {
+    return id1.length > id2.length ? 1 : -1;
+  }
+}
+
+export { compareId };