File advisories for vulnerabilities with upcoming fixes

[Shnatsel]

I am aware of a number of memory safety issues that are slated to get fixes soon™ but do not have a release shipping yet. My life is a bit of a struggle as of late, so I don't have the capacity to follow up on them properly. I'm dumping them here so that someone else could follow up on them and issue advisories.

• Custom Cell implementation is unsound actix/actix-net#160
• UB due to unsafe pinning in actix-codec actix/actix-net#91
• Undefined behavior due to unsafe pinning of BodyStream actix/actix-web#1321
• ComponentBytes is unsound kornelski/rust-rgb#35
• DecompressScanlines::read_scanlines is unsound ImageOptim/mozjpeg-rust#10

[pinkforest]

I drafted the last one for mozjpeg:
#1389