Migrate Cypress (E2E) tests to Vite and TypeScript

This commit progresses the migration from Vue CLI to Vite (#230).

TypeScript migration:

- Convert JavaScript Cypress tests and configurations to TypeScript.
- Introduce `tsconfig.json` for Cypress, following official
  recommendation.

Test execution:

- Use Cypress CLI to run the tests.
- Rename Cypress commands to reflect official naming conventions.
- Start Vue server prior to Cypress execution, using
  `start-server-and-test` package based on official documentation.
- Remove dependency on Vue CLI plugin ((`@vue/cli-plugin-e2e-cypress`).

Configuration standardization (based on Cypress docs):

- Delete unused `plugins/` directory.
- Move test (spec) files to to the root directory.
- Add official ESLint plugin (`eslint-plugin-cypress`).

Changes for importing `vite.config.ts` into `cypress.config.ts`:

- Add TypeScript import assertations to files importing JSON files.
- Use ESM friendly way instead of `__dirname` to solve `ReferenceError:
  __dirname is not defined in ES module scrope`.

Other changes:

- Simplify comments in placeholder files.
- Create Cypress specific `.gitignore` for enhanced maintainability,
  clarity and scalability.
- Remove redundant `vue.config.cjs`.

cypress.config.ts

@@ -1,15 +1,15 @@
 import { defineConfig } from 'cypress';
-import setupPlugins from './tests/e2e/plugins/index';
+import ViteConfig from './vite.config';
+
+const CYPRESS_BASE_DIR = 'tests/e2e/';
 
 export default defineConfig({
-  fixturesFolder: 'tests/e2e/fixtures',
-  screenshotsFolder: 'tests/e2e/screenshots',
-  videosFolder: 'tests/e2e/videos',
+  fixturesFolder: `${CYPRESS_BASE_DIR}/fixtures`,
+  screenshotsFolder: `${CYPRESS_BASE_DIR}/screenshots`,
+  videosFolder: `${CYPRESS_BASE_DIR}/videos`,
   e2e: {
-    setupNodeEvents(on, config) {
-      return setupPlugins(on, config);
-    },
-    specPattern: 'tests/e2e/specs/**/*.cy.{js,jsx,ts,tsx}',
-    supportFile: 'tests/e2e/support/index.js',
+    baseUrl: `http://localhost:${ViteConfig.server.port}/`,
+    specPattern: `${CYPRESS_BASE_DIR}/**/*.cy.{js,jsx,ts,tsx}`, // Default: cypress/e2e/**/*.cy.{js,jsx,ts,tsx}
+    supportFile: `${CYPRESS_BASE_DIR}/support/e2e.ts`,
   },
 });