Add TI ISO674x series

Adds the ISO674x General-Purpose Quad-Channel Digital Isolator series chips

Datasheet: https://www.ti.com/lit/ds/symlink/iso6740.pdf

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• Remove the instructional content of this template
• Provide a URL to a datasheet for the symbol(s) you are contributing
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• Ensure that the associated footprints match the official footprint library
  • A new fitting footprint must be submitted if the library does not yet contain one.
• If there are matching footprint PRs, provide link(s) as appropriate
• Check the output of the automated check scripts - fix any errors as required
• Give a reason behind any intentional library convention rule violation.