feat: OpenSearch (#9780)

* added OpenSearch

* prettier stuff

* moved opensearch to layout

* Fix build errors

* Revert "moved opensearch to layout"

* Add trailing space

---------

Co-authored-by: Puru <devpuruvj@gmail.com>

sites/svelte.dev/src/app.html

@@ -11,6 +11,13 @@
 		<meta name="twitter:site" content="@sveltejs" />
 		<meta name="twitter:creator" content="@sveltejs" />
 
+		<link
+			rel="search"
+			type="application/opensearchdescription+xml"
+			href="/opensearch.xml"
+			title="Svelte"
+		/>
+
 		<!-- add inline style and blocking script to prevent content flash/jump -->
 		<style>
 			.ts-version {

sites/svelte.dev/static/opensearch.xml

@@ -0,0 +1,10 @@
+<OpenSearchDescription xmlns="http://a9.com/-/spec/opensearch/1.1/"
+    xmlns:moz="http://www.mozilla.org/2006/browser/search/">
+    <ShortName>Svelte</ShortName>
+    <Description>Search Svelte</Description>
+    <InputEncoding>UTF-8</InputEncoding>
+    <Image width="128" height="128" type="image/png">https://svelte.dev/favicon.png</Image>
+    <Url type="text/html" method="get"
+        template="https://svelte.dev/search?q={searchTerms}" />
+    <moz:SearchForm>https://svelte.dev/search</moz:SearchForm>
+</OpenSearchDescription>