add RevokeToken via access_token method.

[dlipford360]

hey! I needed a revokeToken method and forked your repo and made one. I tested it and it works. maybe unique_id could be renamed to access_token. it just happened that way when I made it. On my implementation it's use kinda goes like

• step 1 -> authorization_code passed to BE. step 2- > below

//this code is ran. gets accessToken, then uses it to revoke
const access_token = await this.appleAuth.accessToken(authorization_code) 
const revoked_token = await this.appleAuth.revokeToken(
        access_token.access_token,
      )