Add test with zero.

Author: cristianoc

jscomp/gentype_tests/typescript-react-example/src/Unboxed.gen.tsx

@@ -16,7 +16,7 @@ export type r2 = string;
 
 export type t = number[] | number | ((_1:number) => number);
 
-export type tabIndex = "0" | "1";
+export type tabIndex = "0" | "1" | 0;
 
 export const testV1: (x:v1) => v1 = UnboxedBS.testV1;
 

jscomp/gentype_tests/typescript-react-example/src/Unboxed.res

@@ -18,7 +18,7 @@ type r2 = B({g: string})
 type t = Array(array<int>) | Record({x: int}) | Function((. int) => int)
 
 @genType
-type tabIndex = | @as("0") Activity | @as("1") UserKeyword
+type tabIndex = | @as("0") Activity | @as("1") UserKeyword | @as(0) NumZero
 
 @genType
 let a = Activity