formatter: json formatter should be native

[azu]

-f json is the result of textlint's format.
We should return secretlint results as json insteadof it.

Currently, @secretlint/formatter is wrapper of textlint's formatter #10
As soon as, json formatter will be replaced native formatter.
Because, json formatter present raw results data.

[azu]

fixed in #527

[azu]

const before = [{
  "filePath": "[SNAPSHOT]/input.txt",
  "messages": [{
    "ruleId": "example",
    "index": 8,
    "line": 1,
    "column": 8,
    "range": [8, 14],
    "loc": {
      "start": { "line": 1, "column": 8 },
      "end": { "line": 1, "column": 14 },
    },
    "severity": 1,
    "message": "[message-id] warning found secret: SECRET",
    "data": { "ID": "SECRET" },
    "type": "lint",
  }, {
    "ruleId": "example",
    "index": 8,
    "line": 1,
    "column": 8,
    "range": [8, 14],
    "loc": {
      "start": { "line": 1, "column": 8 },
      "end": { "line": 1, "column": 14 },
    },
    "severity": 2,
    "message": "[message-id] error found secret: SECRET",
    "data": { "ID": "SECRET" },
    "type": "lint",
  }, {
    "ruleId": "parent > example",
    "index": 8,
    "line": 1,
    "column": 8,
    "range": [8, 14],
    "loc": {
      "start": { "line": 1, "column": 8 },
      "end": { "line": 1, "column": 14 },
    },
    "severity": 2,
    "message": "[message-id] error found secret: SECRET",
    "data": { "ID": "SECRET" },
    "type": "lint",
  }],
}, { "filePath": "[SNAPSHOT]/input.no-secret.txt", "messages": [] }];
const after = [{
  "filePath": "[SNAPSHOT]/input.txt",
  "sourceContent": "THIS IS SECRET SOURCE\n",
  "sourceContentType": "text",
  "messages": [{
    "data": { "ID": "SECRET" },
    "type": "message",
    "message": "warning found secret: SECRET",
    "messageId": "message-id",
    "range": [8, 14],
    "loc": {
      "start": { "line": 1, "column": 8 },
      "end": { "line": 1, "column": 14 },
    },
    "ruleId": "example",
    "severity": "warning",
  }, {
    "data": { "ID": "SECRET" },
    "type": "message",
    "message": "error found secret: SECRET",
    "messageId": "message-id",
    "range": [8, 14],
    "loc": {
      "start": { "line": 1, "column": 8 },
      "end": { "line": 1, "column": 14 },
    },
    "ruleId": "example",
    "severity": "error",
  }, {
    "data": { "ID": "SECRET" },
    "type": "message",
    "message": "error found secret: SECRET",
    "messageId": "message-id",
    "range": [8, 14],
    "loc": {
      "start": { "line": 1, "column": 8 },
      "end": { "line": 1, "column": 14 },
    },
    "ruleId": "example",
    "ruleParentId": "parent",
    "severity": "error",
  }],
}, {
  "filePath": "[SNAPSHOT]/input.no-secret.txt",
  "sourceContent": "THIS IS PUBLIC SOURCE\n",
  "sourceContentType": "text",
  "messages": [],
}];