test: add TS types

tests/ModalLarge.test.svelte

@@ -0,0 +1,17 @@
+<script lang="ts">
+  import { Modal } from "../types";
+</script>
+
+<Modal
+  size="lg"
+  open
+  modalHeading="Create database"
+  primaryButtonText="Confirm"
+  secondaryButtonText="Cancel"
+  on:click:button--secondary
+  on:open
+  on:close
+  on:submit
+>
+  <p>Create a new Cloudant database in the US South region.</p>
+</Modal>