Emit more event about related filename and task type.

[DiscreteTom]

E.g. maybe TransferMonitor can do something like:

this.emit('ignore', filename)
this.emit('start', filename)
this.emit('done', filename)

[mikenikles]

I came here to open the same issue, mainly for the this.emit('done', filename); event.

I'm working on a project that requires post-processing of files synced from Cloudflare R2 to a local file system. There are thousands of files and sync may take a while, hence I'd love to start the post-processing as soon as a file is synced.

#44 is a suggestion of how we could achieve that. Please let me know what you think 😊.