Add Placeholder for Articles Index Page

[taeho1031]

• [ ] There is a file called 'ArticlesIndexPage.js' in the 'src/main/pages/Articles' directory.
• [ ] The file export a react component with a basic layout, a title 'Articles', and placeholder text.
• [ ] In 'App.js', there is a route linking the path '/articles/list' to 'ArticlesIndexPage'