feat: add RegisterResult component, ESLint config, and vue.config.js for project setup

- Created a new RegisterResult.vue component for displaying registration success.
- Added ESLint configuration for unit tests in the tests directory.
- Implemented vue.config.js for webpack configuration, including theme color support and proxy settings for development.

frontend_vue/postcss.config.js

@@ -0,0 +1,5 @@
+module.exports = {
+  plugins: {
+    autoprefixer: {}
+  }
+}