Allow array of strings for issuer option

[manyike]

Describe the Feature

When verifying tokens the JWT library which is used in this project support issuer as a string or an array of strings. To align this project with that I suggest allowing issuer as a string or an array of strings. This functionality comes in handy in cases where we setup azure b2c custom domains in this scenario both the default azure domain and the custom domain should be regarded as valid issuers.

Suggested Solution

After taking a look at the code it looks like the change should be simple enough and I'm happy to push a pull request. Essentially we just need to change VerifyOptions interface to look like below.

export interface VerifyOptions {
  ...

  issuer: string | string[];

  ...
}

Other Information

n/a