fix: do not parse mpeg-ts files as typescript files

[KnisterPeter]

MPEG-TS files consist of frames each 188 bytes long.
These files should not be parsed as typescript files
and therefore we look into the first 50 frames and
check if we find a 'valid' header.

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Fixes #21136

[KnisterPeter]

@mhegazy @RyanCavanaugh The tests are still missing here, but if you don't mind I would love to get some feedback if the direction of this fix is correct.

[RyanCavanaugh]

Apologies for the delay here.

I think we need to optimize this for incurring the absolute minimum overhead in the common case where none of the files are MPEGs. Specifically, that means the order of operations should be:

• Read the file as normal
• If the length is enormous (20 MB?) then check for the signalling bytes
• If the file is determined to be a transport stream, then fail in some reasonably graceful manner (doesn't have to be perfect since this should never be occurring except once by mistake)

[RyanCavanaugh]

Closing due to inactivity