Service worker

[gaurave]

• Adds A service worker
• Allows serving of local urls via service worker.
• The url schema to access local urls is http://host/local/fileSystemName/path

TODOs

• Make the connection between the page and service worker reliable.
• Add timeout for the failed request.

@rpaquay PTAL thanks.

[gaurave]

@rpaquay PTAL

[rpaquay]

lgtm after nits addressed.