Collaborative document editing tools are widely used in both professional and academic workplaces. While these tools provide some accessibility features, it is still challenging for blind users to gain collaboration awareness that sighted people can easily obtain using visual cues (e.g., who edited or commented where and what in the document). To address this gap, we present CollabAlly, a browser extension that makes extractable collaborative and contextual information in document editing accessible for blind users. With CollabAlly, blind users can easily access collaborators' information, track real-time or asynchronous content and comment changes, and navigate through these elements. In order to convey this complex information through audio, CollabAlly uses voice fonts and spatial audio to enhance users' collaboration awareness in shared documents. Through a series of pilot studies with a coauthor who is blind, CollabAlly's design was refined to include more information and to be more compatible with existing screen readers.