DecorationAttachmentRenderingOptions.hoverMessage does not work in browser extension

[emidoots]

The code discussions extension provides a hoverMessage in all attachments it creates, but they only show up on Sourcegraph and not e.g. on GItHub with the browser extension.

https://github.com/sourcegraph/sourcegraph-extension-api/blob/master/src/sourcegraph.d.ts#L453-L454