Web renderer: Support more containers

[JonnyBurger]

Currently only "mp4" and "webm" containers are supported (defined in WebRendererContainer).

• Figure out which other containers make sense and support for them
• If we already have docs (at time of writing we don't), update them
• Make an audio-only export work - for this, the renderMediaOnWeb() mechanic has to be changed because currently it always takes a screenshot. The videoEnabled variable is hardcoded to true, it should be set based on whether the specified container is an audio-only codec (tags like <Video> will skip work based on this variable), and any screenshotting should be skipped.
• Update packages/studio/src/components/RenderModal/WebRenderModal.tsx to add an "audio" tab analogue to the ServerRenderModal.
• Remove // TODO: More containers from code.