feat: ability to specify unique values

[hichemfantar]

feat: ability to specify unique values

[juliusmarminge]

Should be solved with a .refine with #169

[juliusmarminge]

Can also do it today with just a check after the createEnv call, no?

const env = createEnv({
  server: {
    PORT_1: z.coerce.number(),
    PORT_2: z.coerce.number(),
  },
  runtimeEnv: process.env,
});

const allPorts = [env.PORT_1, env.PORT_2];
if (new Set(allPorts).size !== allPorts.length) {
  throw new Error("All ports must be unique, got " + JSON.stringify(allPorts));
}