Add example of JSON pointers using array indexes.

[kenfdev]

A very small change to the docs but I found the current explanation a bit obscure.

https://www.openpolicyagent.org/docs/latest/decision-logs/#masking-sensitive-data

For people who are familiar with JSON Pointers, I thinks it's obvious to use array indices, but for others, maybe it's better to show examples.

In addition, was thinking about adding a detailed example like below but left it as a simple phrase.

Things I've tested

mask["/input/secrets/0"]

Result (Example of pointers to array not taking effect)

{
  "decision_id": "6b8fda76-ae6c-4b63-b1bb-34384c8c3c7c",
  "erased": ["/input/password"],
  "input": {
    "name": "bob",
    "resource": "user",
    "secrets": [{ "value": "secret1" }, { "value": "secret2" }]
  },
  "labels": {
    "id": "75f51a30-3906-46b5-bb1e-4da3496de0f6",
    "version": "0.13.0-dev"
  },
  "level": "info",
  "metrics": {
    "timer_rego_module_compile_ns": 301,
    "timer_rego_module_parse_ns": 508,
    "timer_rego_query_compile_ns": 433436,
    "timer_rego_query_eval_ns": 64411,
    "timer_rego_query_parse_ns": 476805,
    "timer_server_handler_ns": 3727650
  },
  "msg": "Decision Log",
  "path": "foo/allow",
  "requested_by": "172.17.0.1:51764",
  "result": true,
  "time": "2019-06-18T14:16:36Z",
  "timestamp": "2019-06-18T14:16:36.15410267Z"
}

mask["/input/secrets/0/value"]

Result(Example of pointer to object inside an array which is allowed)

{
  "decision_id": "8f19f901-11d4-47eb-8ba0-3955630161b4",
  "erased": ["/input/secrets/0/value", "/input/password"],
  "input": {
    "name": "bob",
    "resource": "user",
    "secrets": [{}, { "value": "secret2" }]
  },
  "labels": {
    "id": "602eba22-876c-48b5-a484-ce549579b54b",
    "version": "0.13.0-dev"
  },
  "level": "info",
  "metrics": {
    "timer_rego_module_compile_ns": 265,
    "timer_rego_module_parse_ns": 414,
    "timer_rego_query_compile_ns": 202855,
    "timer_rego_query_eval_ns": 52394,
    "timer_rego_query_parse_ns": 659617,
    "timer_server_handler_ns": 2423068
  },
  "msg": "Decision Log",
  "path": "foo/allow",
  "requested_by": "172.17.0.1:51768",
  "result": true,
  "time": "2019-06-18T14:17:29Z",
  "timestamp": "2019-06-18T14:17:29.265131767Z"
}

I would appreciate any feedback :)
Thank you!

[tsandall]

LGTM

[tsandall]

Thanks @kenfdev !