Add avif and webm to the list of supported extensions

[goekce]

Fixes #2996

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Latest commit: 63da9d4

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[goekce]

Related PR in the default theme: jupyter-book/myst-theme#926

[Copilot]

Pull request overview

This PR updates myst-cli’s recognized media extensions so AVIF images (.avif) and WebM videos (.webm) are treated as supported assets during site builds, addressing the “Unsupported image extension” error described in #2996.

Changes:

• Add .avif and .webm to the ImageExtensions enum and include .webm in KNOWN_VIDEO_EXTENSIONS.
• Extend the default site-build (WEB_IMAGE_EXTENSIONS) allowlist to include AVIF and WebM.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/myst-cli/src/utils/resolveExtension.ts	Adds avif/webm to the canonical extension lists used across CLI transforms.
packages/myst-cli/src/process/site.ts	Allows .avif and .webm by default for site processing to avoid unsupported-extension errors.

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