✅(y-provider) add tests for y-provider server

We add jest tests for the y-provider server.
The CI will be able to run the tests.

src/frontend/servers/y-provider/.eslintrc.cjs

@@ -1,6 +1,6 @@
 module.exports = {
   root: true,
-  extends: ['impress/next'],
+  extends: ['impress/jest', 'impress/next'],
   parserOptions: {
     tsconfigRootDir: __dirname,
     project: ['./tsconfig.json'],