[css][html] SVG language support

[octref]

Currently, we have no SVG support:

• In HTML, SVG tags don't receive auto completion
• In CSS, SVG attributes don't receive auto completion
• Syntax highlighting are problematic for both SVG tags/attributes in HTML/CSS
• Emmet do not get SVG completions

However, with custom tag/property support in HTML/CSS, we should be able to trivially write a SVG package that describes the set of tags/attributes for SVG, and let HTML/CSS language services do the support work.

• Web Components support in HTML files #62976
• Custom Properties contribution for CSS #64164

[chpxu]

Since SVG is an XML variant, would support for XML be included? Or would that have to be a request under Atom's XML package?

[octref]

This issue only concerns SVG. VS Code has some support for XML, and there are extensions for XML too: https://marketplace.visualstudio.com/search?term=xml&target=VSCode&category=All%20categories&sortBy=Relevance

[hinell]

Would be nice to have standard emmet abbreviation completion.

[felixfbecker]

<style> tags inside SVG files also have no CSS syntax highlighting or autocompletion, but do in HTML files.

[tjx666]

any progress? It would be great to support emmet syntax in svg. By using following setting, I can get emmet suggestion, but can't get svg specific tag suggestion

"emmet.includeLanguages": {
        "svg": "html"
 },