Rework modal header structure

src/app/components/RoomCreate.svelte

@@ -8,6 +8,8 @@
   import Button from "@lib/components/Button.svelte"
   import Icon from "@lib/components/Icon.svelte"
   import ModalHeader from "@lib/components/ModalHeader.svelte"
+  import ModalTitle from "@lib/components/ModalTitle.svelte"
+  import ModalSubtitle from "@lib/components/ModalSubtitle.svelte"
   import ModalFooter from "@lib/components/ModalFooter.svelte"
   import RoomForm from "@app/components/RoomForm.svelte"
   import {makeSpacePath} from "@app/util/routes"
@@ -22,14 +24,10 @@
 <RoomForm {url} {onsubmit}>
   {#snippet header()}
     <ModalHeader>
-      {#snippet title()}
-        <div>Create a Room</div>
-      {/snippet}
-      {#snippet info()}
-        <div>
-          On <span class="text-primary">{displayRelayUrl(url)}</span>
-        </div>
-      {/snippet}
+      <ModalTitle>Create a Room</ModalTitle>
+      <ModalSubtitle>
+        On <span class="text-primary">{displayRelayUrl(url)}</span>
+      </ModalSubtitle>
     </ModalHeader>
   {/snippet}
   {#snippet footer({loading})}