WIP: add PRONOM export

[ross-spencer]

Very broad strokes export to PRONOM. Quick wins tonight that need optimising are the IS/ENDSWITH/STARTSWITH/CONTAINS/EXISTS options. If we can get those working it's a pretty good start.

TODO:

• output baseline JSON identifier too with optimizations (fmt/81)
• convert all sigs document those which don't work.
• documentation.
• sensible parameterization of defaults.
• document new regex that PRONOM could support.
• consider fido export.
• output defaults for encodings.
• process JSON basic types -- at least list, and dict...

First working signature file

<?xml version="1.0" ?>
<FFSignatureFile xmlns="http://www.nationalarchives.gov.uk/pronom/SignatureFile" Version="1" DateCreated="2025-11-24T21:24:32Z">
  <InternalSignatureCollection>
    <InternalSignature ID="1" Specificity="Specific">
      <ByteSequence Reference="BOF" Sequence="{0-4095}7B" MinOffset="0" MaxOffset="4095"/>
      <ByteSequence Reference="VAR" Sequence="226E616D6522{0-10}3A" MinOffset="" MaxOffset=""/>
      <ByteSequence Reference="VAR" Sequence="226C6F636B66696C6556657273696F6E22{0-10}3A" MinOffset="" MaxOffset=""/>
      <ByteSequence Reference="VAR" Sequence="227061636B6167657322{0-10}3A" MinOffset="" MaxOffset=""/>
      <ByteSequence Reference="EOF" Sequence="7D{0-4095}" MinOffset="0" MaxOffset="4095"/>
    </InternalSignature>
  </InternalSignatureCollection>
  <FileFormatCollection>
    <FileFormat ID="1" Name="JavaScript Package Lock" PUID="jrid:0001" Version="" MIMEType="TODO" FormatType="structured text">
      <InternalSignatureID>1</InternalSignatureID>
    </FileFormat>
  </FileFormatCollection>
</FFSignatureFile>