chore: restructure repo into sub folders

api/jest.config.js

@@ -0,0 +1,15 @@
+module.exports = {
+  preset: 'ts-jest/presets/js-with-ts',
+  testEnvironment: 'node',
+  // FIXME: improve test coverage and uncomment below lines
+  // coverageThreshold: {
+  //   global: {
+  //     branches: 80,
+  //     functions: 80,
+  //     lines: 80,
+  //     statements: -10
+  //   }
+  // },
+  collectCoverageFrom: ['src/**/{!(index),}.ts'],
+  testPathIgnorePatterns: ['/node_modules/', '<rootDir>/build/']
+}