Show warning for non-nip29 relays

src/app/components/InfoMissingRooms.svelte

@@ -0,0 +1,34 @@
+<script lang="ts">
+  import Button from "@lib/components/Button.svelte"
+  import Link from "@lib/components/Link.svelte"
+  import ModalHeader from "@lib/components/ModalHeader.svelte"
+  import {PLATFORM_NAME} from "@app/state"
+</script>
+
+<div class="column gap-4">
+  <ModalHeader>
+    {#snippet title()}
+      <div>Where did my rooms go?</div>
+    {/snippet}
+  </ModalHeader>
+  <p>
+    You might have noticed that old rooms have disappeared from navigation. {PLATFORM_NAME} is still
+    under heavy development, which means that we occasionally have to make breaking changes. In this
+    case, we've changed how rooms work in {PLATFORM_NAME} to be more fully compatible with other NIP
+    29 clients, like <Link external class="link" href="https://chachi.chat">Chachi</Link> and
+    <Link external class="link" href="https://0xchat.com">0xChat</Link>.
+  </p>
+  <p>
+    This one is particularly annoying, but there is a migration path. To start with, your messages
+    are all still available under the "Chat" tab - all conversations have just been merged together.
+  </p>
+  <p>
+    Next, if you run a relay please upgrade to a version that supports NIP 29. {PLATFORM_NAME} works
+    best with the latest version of <Link
+      external
+      class="link"
+      href="https://github.com/coracle-social/frith">Frith</Link
+    >, which includes a migrate script to upgrade your old rooms into NIP 29 compatible rooms.
+  </p>
+  <Button class="btn btn-primary" onclick={() => history.back()}>Got it</Button>
+</div>