Support for constants

[d4h0]

Hi,

I tried the following:

#[typeshare::typeshare]
const SHARED_VAR: &str = "value";

...hoping that I could use this to define some shared constants in one place, but that doesn't seem to be supported.

There also wasn't an error message, which isn't ideal, I think.

[snowsignal]

I think this could be a useful feature! However, we would probably have to limit the scope of this change to numeric and string constants for now.

[d4h0]

@InquisitivePenguin: That seem reasonable. Booleans probably also could be supported easily.

[dwosk]

@InquisitivePenguin any update on your PR? Support for Rust &str constants would be really useful for us, thanks!

[snowsignal]

@dwosk Sorry about the delay - support for this should be ready soon.