Allow to suppress '<' validation for attribute values when error suppression is enabled

[kasthack]

New Feature Proposal

Description

Allow to bypass opening bracket validation when XmlParserOptions.IsSuppressingErrors is set to true. Just a single-line change

Background

Provide any additional background for the feature. e.g., user scenarios.

Parsing technically malformed XML-elements that contain opening diamond brackets in attributes.

• This is a somewhat known issue
• '<' handling is buried deep in .net's built-in System.Xml.XmlReader, so invalid documents can't be parsed without writing a substantial amount of code.
• Correcting the input on the fly basically requires writing an own tokenizer which seems quite excessive for something as simple as ignoring an opening bracket that should be escaped.
• Documentation for XmlParserOptions.IsSuppressingErrors explicitly states, that enabling this option may break the document and it's disabled by default anyway, so changing this behavior won't be an unpleasant surprise for the users.

Currently, trying to parse <condition value="a < b" /> would raise an exception even if error suppression is enabled. Proposed change would allow to successfully parse it.

[FlorianRappl]

Sounds great. Could you make the PR @kasthack ? Then we could fit it in 0.13!

Thanks a lot 🍻!

[FlorianRappl]

Landed in devel.