Add more demo application implementation (#27)

demo/README.md

demo/assets/.htaccess.ejs

demo/assets/Makefile

demo/assets/common.metadata.json

demo/assets/dbp-toolkit-demo.topic.metadata.json.ejs

demo/assets/file-handling.metadata.json

demo/assets/icon-192.png

demo/assets/icon-512.png

...assets/knowledge-base-web-page-element-view.metadata.json

demo/assets/logo.svg

demo/assets/manifest.json

demo/assets/silent-check-sso.html

demo/package.json

demo/rollup.config.js