web: Handle missing OffscreenCanvas for canvas font renderer

[kjarosh]

Some browsers might not support OffscreenCanvas. This patch makes sure we handle the situation properly.

[n0samu]

To clarify, do we fall back to our normal method of font rendering in this case?

[kjarosh]

To clarify, do we fall back to our normal method of font rendering in this case?

Yes, the default font is always the fallback when enabled.

[danielhjacobs]

Specifically it will go to this path, right?

ruffle/web/src/ui.rs

Lines 335 to 340 in 7e90df6

	Err(e) => {
	tracing::error!(
	"Failed to set up canvas font renderer for font \"{}\": {e:?}",
	query.name
	)
	}