Add warmup paper cold shower.

As requested, here's the PR to add our warmup paper to your list. Thanks.

[*] I have followed the code of conduct.
[*] I have followed the contributing guidelines and used the proper item format.
[*] This is not a duplicate.
[*] The resource is free.
[*] The resource is rigorous because: published in a peer reviewed and respected academic conference.
[*] The resource is not obnoxious, condescending, etc.
[*] My writup is respectful of both sides.
[*] I've added reasonable caveats.
[*] I've noted if the resource is a video, pdf, etc.

hwayne / awesome-cold-showers