Make FeedSpider 2 a PWA

[codepoet80]

The following changes allow FeedSpider to work as a modern Progress Web App (PWA) on iOS, Android and Chrome...

• Bumped version, added manifest.json and stub service worker. Added appropriate icon references in manifest and index.html. Added metatags for use on iOS.
• Added stub serviceworker so Chrome will offer the "Install" option
• Moved InoReader to a (now public) nginx reverse proxy to allow CORS, so that it will load on a modern browser. Other back-ends not yet supported (except on older devices that don't care about CORS). Example nginx config file included.
• Other back-ends to be supported in future PRs.

Try it out at https://feedspider.online/app

[codepoet80]

I don't know how to revise a PR to make those changes, so I'll close this PR and submit a new one with some other modifications we're making for newer LuneOS support.