docs: document jest troubleshooting (#382)

example/jest.config.example.js

@@ -0,0 +1,30 @@
+const { createConfig } = require('@edx/frontend-build');
+
+module.exports = createConfig('jest', {
+  setupFiles: [
+    '<rootDir>/src/setupTest.js',
+  ],
+  setupFilesAfterEnv: [
+    '<rootDir>/src/setupTestEnv.js',
+  ],
+  collectCoverageFrom: [
+    "**/*.{js,jsx}",
+  ],
+  testMatch: [
+    '**/specs/**/*.spec.(js|jsx)|**/__tests__/*.(js|jsx)|**/specs/*.spec.(js|jsx)',
+  ],
+  roots: [
+    '<rootDir>src/',
+  ],
+  coveragePathIgnorePatterns: [
+    'src/setupTestEnv.js',
+    'src/setupTest.js',
+    'jest.config.js',
+    'src/i18n',
+    '/node_modules/',
+    '/specs/'
+  ],
+  moduleNameMapper: {
+    '^lodash-es$': 'lodash',
+  },
+});