[web-client] simple theme: build & development env based on vite.

Vite is a build tool, it consists of two major parts [1]:

- A dev server that provides rich feature enhancements over native ES modules,
  for example extremely fast Hot Module Replacement (HMR).

- A build command that bundles your code with Rollup, pre-configured to output
  highly optimized static assets for production.

[1] https://vite.dev/guide/

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

.github/dependabot.yml

@@ -12,11 +12,11 @@ updates:
       prefix: "[upd] pypi:"
 
   - package-ecosystem: "npm"
-    directory: "/searx/static/themes/simple"
+    directory: "/client/simple"
     schedule:
       interval: "weekly"
       day: "friday"
     open-pull-requests-limit: 5
     target-branch: "master"
     commit-message:
-      prefix: "[upd] npm:"
+      prefix: "[upd] web-client (simple):"