Use relative base path for vite build

Allows Element Call to be served from a subdirectory (e.g. /widgets/element-call/
in Element Web) without breaking dynamic imports for locales, workers, and other
assets that were previously using absolute paths.

Signed-off-by: Ryan Emmick <ryanemmick4@gmail.com>

vite.config.ts

@@ -102,6 +102,7 @@ export default ({
   console.log("Allowed vite paths:", allow);
 
   return {
+    base: "./",
     server: {
       port: 3000,
       fs: { allow },