test: add test configuration

jest.config.js

@@ -0,0 +1,20 @@
+const { createDefaultPreset } = require("ts-jest");
+
+const tsJestTransformCfg = createDefaultPreset().transform;
+
+/** @type {import("jest").Config} **/
+module.exports = {
+  testEnvironment: "node",
+  transform: {
+    ...tsJestTransformCfg,
+    "^.+\\.tsx?$": [
+      "ts-jest",
+      {
+        isolatedModules: true,
+      },
+    ],
+  },
+  moduleNameMapper: {
+    "\\.(png|jpg|jpeg|gif|svg)\\?asset$": "<rootDir>/__mocks__/fileMock.js",
+  },
+};

package.json

@@ -34,13 +34,16 @@
     "@types/auto-launch": "^5.0.5",
     "@types/discord-rpc": "^4.0.9",
     "@types/electron-squirrel-startup": "^1.0.2",
+    "@types/jest": "^30.0.0",
     "@typescript-eslint/eslint-plugin": "^5.62.0",
     "@typescript-eslint/parser": "^5.62.0",
     "electron": "38.1.2",
     "eslint": "^8.57.1",
     "eslint-plugin-import": "^2.32.0",
+    "jest": "^30.4.2",
     "json-schema-typed": "^8.0.1",
     "prettier": "^3.6.2",
+    "ts-jest": "^29.4.11",
     "typescript": "~4.5.4",
     "vite": "^5.4.20"
   },