Safari can't play videos from media servers that don't support CORS

[nolanlawson]

Follow up to #1590 and #1547.

If the media host doesn't have CORS enabled, then Safari cannot properly support range requests. The reason for this is:

1. There is a bug in WebKit that causes ServiceWorker not to allow range requests to pass through normally.
2. The only known workaround for this issue is to issues a CORS-enabled request to the server, read the bytes, and strip out everything but the requested bytes (i.e. serving a pseudo-range request).
3. But this isn't possible if the server doesn't support CORS, and lots of Mastodon instances use media servers that don't support CORS (e.g. awoo.space).

[nolanlawson]

The WebKit bug was marked fixed in November, perhaps it is released now. Need to check.

[nolanlawson]

Based on the repro steps in https://bugs.webkit.org/show_bug.cgi?id=184447 it appears that this bug still repros for me on iPod Touch running 12.4.5.

[nolanlawson]

This seems fixed in iOS 13.3.