feat: raw identifiers

[gx0r]

I was running into an issue where a struct using a raw identifier like

 #[tsync]
 struct RawIdentifierStruct {
     r#type: String,
 }

would keep the r#type resulting in invalid TypeScript output, e.g.

export interface RawIdentifierStruct {
  r#type: string;
}

With this change,

export interface RawIdentifierStruct {
  type: string;
}

[Wulf]

Looks great, thanks @gx0r