Introduce zip upload

[bnkamalesh]

Allow user to upload a full directory of static pages and assets (zipped)

• Should allow drag & drop of zip file
• Queue the request to process (can use Redis for pub/sub)
• Generate a single new page, and use the new generated ID for setting base URL for the whole site
• inject base tag in all HTML files with newly created URL
• only files of following mime type should be allowed: PNG, JPG, PDF, CSS, JS, HTML, SVG, JSON
• limit zip size to 2.5MB (might have to scan to detect a zip bomb somehow)