Search: use Lit WebComponents (#38)

I'm following the pattern from #37 by myself to test out the framework
and start to feel more comfortable.

---------

Co-authored-by: Anthony Johnson <[email protected]>

Author: humitos

dist/readthedocs-client.js

@@ -95,6 +95,22 @@
                 "branch": "main",
                 "filepath": "/examples/sphinx/docs/index.rst"
             }
+        },
+        "search": {
+            "project": "example",
+            "version": "latest",
+            "api_endpoint": "/_/api/v3/search/",
+            "filters": [
+                [
+                  "Search only in this project",
+                  "project:example/latest"
+                ],
+                [
+                  "Search subprojects",
+                  "subprojects:example/latest"
+                ]
+            ],
+            "default_filter": "subprojects:example/latest"
         }
     }
 }

public/_/readthedocs-config.json

@@ -1,6 +1,7 @@
 import { getReadTheDocsConfig } from "./readthedocs-config";
 import * as notification from "./notification";
 import * as analytics from "./analytics";
+import * as search from "./search";
 import { domReady, isReadTheDocsEmbedPresent } from "./utils";
 
 export function setup() {
@@ -19,6 +20,7 @@ export function setup() {
         const addons = [
           notification.NotificationAddon,
           analytics.AnalyticsAddon,
+          search.SearchAddon,
         ];
 
         for (const addon of addons) {