add complete JWT verification example

[frasertweedale]

10:22 <frphank_> frase: other libraries' "verifyJWT" function takes 2 strings, the JWT and the secret.
10:22 <frphank_> where is this function
10:22 <frphank_> I had to write it
10:39 <frase> wtf, strings.  no wai man
10:40 <frphank_> well I ended up finding the fromOctets and decodeCompact functions eventually so it's not like it 
                 isn't supported
10:40 <frphank_> you just have to puzzle it together yourself

[frasertweedale]

  let jwk = fromOctets . fromString $ "Ge6m8I`5W#f)Z+H]emaPz*/@*@UZ7R;R0/uBRpEVQS]^c5Mf{N@>oIc]~+F+S-m0"
      result = do
        jws <- decodeCompact . L.fromStrict . fromString $ "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpYXQiOjE1MDA2Mjk0NzMsImlzcyI6Inh5eiIsImV4cCI6MTUwMDcxNTg3Mywic3ViIjoyfQ.wTEERJbyRjzBtJY4piJwRE9SL4nJ4Hy87qbel4EEqm8"
        verifyJWS' (jwk :: JWK) (jws :: CompactJWS JWSHeader)
  result <- runExceptT $ result