#read et al "reference capabilities" aren't documented

[SeanTAllen]

#read etc aren't documented in the reference capabilities section and should be

[SeanTAllen]

they are however covered here: https://tutorial.ponylang.io/generics/generic-constraints.html

[matthew-russo]

+1 It also doesn't show up in the tutorial when you search for "#read" which makes it a bit more difficult to find