Cannot use SVGs with <feBlend> in stories

[swissspidy]

Description

#22187 added support for SVGs in stories, but it looks like some elements were missed there.

For example, it is not possible to use <feBlend> in stories, whereas it works just fine in regular AMP pages.

I don't see why it shouldn't be allowed, so seems like an oversight.

Perhaps there are more tags that are missing as well.

Context: In the Web Stories WordPress plugin we'd like to create stories containing an SVG which uses <feBlend>.

Reproduction Steps

1. Open AMP playground
2. Select "AMP for Stories"
3. Insert the SVG below within <amp-story-grid-layer>
4. See validation error

Relevant Logs

The tag 'feblend' may not appear as a descendant of tag 'amp-story-grid-layer'

Browser(s) Affected

No response

OS(s) Affected

No response

Device(s) Affected

No response

AMP Version Affected

2107170150000