Set up automated logic testing.

There's a LOT to keep up with. Best verify these are coded right.

.github/workflows/npm-validate-build.yaml

@@ -25,3 +25,5 @@ jobs:
       run: npm ci
     - name: Building the project
       run: npm run build
+    - name: Verify the logic
+      run: npm run test

jest.config.js

@@ -0,0 +1,12 @@
+/** @type {import('ts-jest').JestConfigWithTsJest} */
+
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'jsdom',
+  moduleNameMapper: {
+    '^@renderer/(.*)': '<rootDir>/src/renderer/src/$1'
+  },
+  transform: {
+    '^.+\\.(ts|tsx)$': [`ts-jest`, { tsconfig: 'tsconfig.web.json' }]
+  }
+}