Add opaque to the list of keywords (if it is)

[Breush]

This does not parse (syntax error):

package main

A :: struct {
    opaque : int,
}

main :: proc() {
}

What does opaque do? (Couldn't find documentation about it.)

If it is a keyword, add it to https://github.com/odin-lang/Odin/wiki/Keywords-and-Operators

[vassvik]

opaque is a recent addition that is used to create a type that is not read or writeable, which is useful to make typesafe handles,

Handle :: opaque i64;

This should indeed be added to the docs/tutorial.

[Breush]

Can we consider to change the syntax to #opaque?

[gingerBill]

opaque was experimental in the first place but I made it a keyword to make it similar to distinct which is also a keyword.