How to best support XML spec?

[Marvin-Brouwer]

We currently have the following feature's lined up in the future:

• [XML] Namespace support #65
• [XML] Escape text values for known xml escape chars #10
• [XML] Do we want to include the full spec? #11

We need some help with these topics.

[XML] Namespace support #65

How do we implement this in a neat way that fits this library.
We want to be careful to not become as clunky as System.Text.Xml but we also want to support the full namespace functionality.
Because we currently have no maintainers that work with XML namespaces regularly, please offer us advice.

[XML] Escape text values for known xml escape chars #10

We just need to do this at some point so that we comply with the spec.
However, what we'd like to discuss is possibly adding the possibility to define custom entity declarations to escape even more characters.

[XML] Do we want to include the full spec? #11

Is it wise to actually implement this full spec?
Most prominently, the Conditional sections(https://www.w3.org/TR/xml/#sec-condition-sect).
But also Doctype.