Parse include!(<path/to/bracketed>)

For example:

    #[cxx::bridge]
    mod ffi {
        extern "C" {
            include!("path/to/quoted");
            include!(<path/to/bracketed>);

            ...
        }
    }

Emitted as:

    #include "path/to/quoted"
    #include <path/to/bracketed>
diff --git a/syntax/mod.rs b/syntax/mod.rs
index 4702a69..88c96e8 100644
--- a/syntax/mod.rs
+++ b/syntax/mod.rs
@@ -23,7 +23,7 @@
 use proc_macro2::{Ident, Span};
 use syn::punctuated::Punctuated;
 use syn::token::{Brace, Bracket, Paren};
-use syn::{Expr, Lifetime, LitStr, Token, Type as RustType};
+use syn::{Expr, Lifetime, Token, Type as RustType};
 
 pub use self::atom::Atom;
 pub use self::derive::Derive;
@@ -32,7 +32,7 @@
 pub use self::types::Types;
 
 pub enum Api {
-    Include(LitStr),
+    Include(String),
     Struct(Struct),
     Enum(Enum),
     CxxType(ExternType),