feat: ✨ stack and display source code (#8)

* feat: ✨ display source code directly without maintaining extra .md files

* fix: 🔧 fix broken test caused by react-markdown

references:
1.facebook/create-react-app#11946
2.https://stackoverflow.com/questions/49263429/jest-gives-an-error-syntaxerror-unexpected-token-export

* fix: update title tag to PPM

* chore: clean up code; update homepage route

* feat: stack and display source code

.eslintrc.js

@@ -54,6 +54,8 @@ module.exports = {
     // reference: https://typescript-eslint.io/rules/no-unused-vars/
     'no-unused-vars': 'off',
     '@typescript-eslint/no-unused-vars': ['error'],
+    'react/jsx-props-no-spreading': 'off',
+    'react/no-unstable-nested-components': ['off', { allowAsProps: true }],
   },
   // https://github.com/import-js/eslint-plugin-import/issues/1615
   settings: {