XML parser for !DOCTYPE does not handle spaces in PubidLiteral

[halfaya]

Prerequisites

• Check that your issue is not already filed:
  https://github.com/leanprover/lean4/issues
• Reduce the issue to a minimal, self-contained, reproducible test case.
  Avoid dependencies to Mathlib or Batteries.
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Description

The functionLean.Data.Xml.Parser.PubidChar does not consume the space character despite it being clearly stated as an allowed character in the referenced https://www.w3.org/TR/xml/#NT-PubidChar :
[13] | PubidChar | ::= | #x20 \| #xD \| #xA \| [a-zA-Z0-9] \| [-'()+,./:=?;!*#@$_%]

Context

This makes it impossible to parse MusicXml (https://github.com/w3c/musicxml), since a typical !DOCTYPE looks like this:
<!DOCTYPE score-partwise PUBLIC "-//Recordare//DTD MusicXML 4.0 Partwise//EN" "http://www.musicxml.org/dtds/partwise.dtd">

Steps to Reproduce

import Lean.Data.Xml
#eval Lean.Xml.parse "<!DOCTYPE a PUBLIC \"b c\" \"d\"><a></a>"

Expected behavior: ok: <a></a>

Actual behavior: error: offset 21: expected: '"'

Versions

4.27.0-rc1
MacOS 15.7.3

Additional Information

Impact