Feat: Add Support for HLS Interstitials - 1st Version

[Nfrederiksen]

This PR intends to resolve #76

However, it should be noted that for it to overwrite the START-DATE value one will need to load the HlsVod with a timeoffset/unixTs (third input argument). eg.

const myTimestamp = Date.now();
const myVod = new HLSVod("http://hlssource.vod.com/assets/master.m3u8", null, myTimestamp, 0, null, {
  forcedDemuxMode: true,
});

Another thing to remember is that this current version of the feature does not pass through VOD playlists-manifests with a daterange-tag under the endlist-tag. This is something the dependency @eyevinn/node-m3u8 will need to support in its parsing first.

What does work is if the VOD playlist-manifest has the daterange-tag anywhere else, above any 'segment'.
eg.

#EXTM3U
#EXT-X-VERSION:6
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-TARGETDURATION:3
#EXT-X-PROGRAM-DATE-TIME:1970-01-01T00:00:00.001Z
#EXT-X-MAP:URI="test-video=256000.m4s"
#EXTINF:10, no desc
test-video=2500000-1.m4s
#EXTINF:10, no desc
test-video=2500000-2.m4s
#EXTINF:10, no desc
test-video=2500000-3.m4s
#EXT-X-DATERANGE:ID="ad1",CLASS="com.apple.hls.interstitial",START-DATE="1970-01-01T00:00:35.001Z",DURATION=15.0,X-ASSET-URI="http://example.com/ad1.m3u8",X-RESUME-OFFSET=0, X-RESTRICT="SKIP,JUMP",X-COM-EXAMPLE-BEACON=123
#EXTINF:10, no desc
test-video=2500000-4.m4s
#EXT-X-ENDLIST