Support range requests

[hannahhoward]

Goals

Support range requests in the service worker, allowing audio and video content to be loaded.

Requires an update to the JS Client once filecoin-saturn/js-client#48 merges

Implementation

• removes audio/video exclusion -- note that while we now support most variants of range requests, we don't support requests for multiple ranges at once (Range: bytes=0-1000, 1500-2000), and we probably should add a check that excludes these requests. I don't believe the browser tends to use this for audio/video though maybe @gruns knows, but it needs further investigation.
• add a function to parse the string syntax of the range header and turn it into the range object that is expected by the JS client
• parse range header in the interceptor and pass it in the options to the JSClient
• unit test for range parsing function

Next Steps

• as stated, probably need to exclude multi-range requests from our worker (we may be able to handle this, but it's non-trivial
• need to update with the new JS client once merged
• this needs multiple levels of testing before we release to clients.