Feature request: ability to individually mute linter errors / inject namespace definitions

[m-stefanski]

I am editing files that rely on a namespace that is injected by consumer application, and it's schema is not reachable from the internet

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:foo="http://foo" version="1.0" extension-element-prefixes="foo">

...

<xsl:variable name="var" select="foo:function-name()"/>

Linter properly detects missing foo:function-name() declatarion, but i know for sure it is correct and want to disable error - ideally for entire foo namespace with possibility to let linter know the proper function definitions.

I looked through the documentation, also some vscode issues that asked for this functionality - with reponses that this behavior should be configured on linter side.

Is there any way to achieve this I am missing - or would it be a new feature?