Add source files: main entry, types, and configuration

jest.config.cjs

@@ -0,0 +1,19 @@
+module.exports = {
+  testEnvironment: 'node',
+  roots: ['<rootDir>/test'],
+  testMatch: ['**/*.spec.ts'],
+  moduleFileExtensions: ['ts', 'js', 'json'],
+  collectCoverageFrom: ['src/**/*.ts', '!src/**/*.d.ts'],
+  coverageDirectory: 'coverage',
+  verbose: true,
+  transform: {
+    '^.+\\.ts$': ['ts-jest', {
+      useESM: true,
+      tsconfig: 'tsconfig.json',
+    }],
+  },
+  moduleNameMapper: {
+    '^(\\.{1,2}/.*)\\.js$': '$1',
+  },
+  transformIgnorePatterns: [],
+};