Support "pub" for structs and traits

[michaeljklein]

Problem

Compiling the following snippet fails with a parsing error:

pub struct Foo {}

error: Unexpected struct, expected one of fn, open
  ┌─ /Users/michaelklein/Coding/noir/name_shadowing_template/library2/src/lib.nr:7:5
  │
7 │ pub struct Foo {}
  │     ------
  │

Likewise, compiling a similar snippet for traits fails with the same error:

pub trait Foo { ..

error: Unexpected trait, expected one of fn, open
   ┌─ /Users/michaelklein/Coding/noir/name_shadowing_template/library2/src/lib.nr:15:5
   │
15 │ pub trait Foo {
   │     -----
   │

Happy Case

Either support pub for struct's or fail with a more informative error message, e.g. the 'pub' keyword is only supported for functions at this time.

Project Impact

Nice-to-have

Impact Context

No response

Workaround

None

Workaround Description

No response

Additional Context

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response