Update inclusion_tips.md

I assume these standards are being passed among hackathon organizers, but it should be the responsibility of said organizers to pass them along to sponsors. A Microsoft employee once asked me "why did you of all people choose to come here?", and I've seen far too many "booth babes" collecting resumes.

Also, v-neck shirts are just a personal preference of mine and from talking to others they seem more popular among girls than crew necks, but just having female shirts in general would be awesome.