add intro server/api code

codeExamples/week2/serverCode/apisIntro/api-demo/.gitignore

codeExamples/week2/serverCode/apisIntro/api-demo/app.js

codeExamples/week2/serverCode/apisIntro/api-demo/bin/www

...amples/week2/serverCode/apisIntro/api-demo/models/book.js

...les/week2/serverCode/apisIntro/api-demo/package-lock.json

...Examples/week2/serverCode/apisIntro/api-demo/package.json

...les/week2/serverCode/apisIntro/api-demo/public/index.html

...erverCode/apisIntro/api-demo/public/stylesheets/style.css

...s/week2/serverCode/apisIntro/api-demo/routes/api/books.js

...mples/week2/serverCode/apisIntro/api-demo/routes/index.js

...mples/week2/serverCode/apisIntro/api-demo/routes/users.js

...amples/week2/serverCode/apisIntro/express-demo/.gitignore

codeExamples/week2/serverCode/apisIntro/express-demo/app.js

codeExamples/week2/serverCode/apisIntro/express-demo/bin/www

...week2/serverCode/apisIntro/express-demo/package-lock.json

...ples/week2/serverCode/apisIntro/express-demo/package.json

...rCode/apisIntro/express-demo/public/stylesheets/style.css

...s/week2/serverCode/apisIntro/express-demo/routes/index.js

...s/week2/serverCode/apisIntro/express-demo/routes/users.js

...s/week2/serverCode/apisIntro/express-demo/views/error.pug