Implement BitOr for common enum types

[QueenOfSquiggles]

Hey hey. Enum flags could be more intuitive to use if implementing the BitOr trait, which enables support for cases such as:

.connect_ex( /* */ )
  .flags(ConnectFlags::DEFERRED | ConnectFlags::ONE_SHOT)
  .done();

further docs for this trait are available here

A potential implementation could look like:

impl BitOr for ENUM_STRUCT {
  type Output = i32; // or other via type

  fn bitor(self, rhs: Self) -> Self::Output {
    self.to_godot() | rhs.to_godot() 
    // if the via type implements BitOr, this can be used. Else ".ord()" may be needed
  }
}

[Bromeon]

BitOr is already implemented, see https://godot-rust.github.io/docs/gdext/master/godot/classes/object/struct.ConnectFlags.html?search=BitOr.

ConnectFlags may be marked as enum rather than bitfield in the GDExtension API? In that case we'd need to special-case it.

[Bromeon]

Closed because it's not a missing BitOr issue, but a badly defined ConnectFlags in Godot. I can see if a PR is possible for that, although it might be a breaking change and would have to wait until v0.3.

[Bromeon]

@QueenOfSquiggles I changed the classification of ConnectFlags to bitfield via manual override.
It now supports BitOr: #1002

If you have a chance, could you see if this would work for you?
Do you encounter breaking changes? If yes, just imports or others?