Add json formatting

ghokin/fixtures/json.expected.feature

@@ -0,0 +1,11 @@
+Feature: A Feature
+
+  Background:
+    Given a thing
+      """json
+      {
+        "this": "is a json doc string",
+        "but": "with a newline in the middle"
+      }
+      """
+

ghokin/fixtures/json.input.feature

@@ -0,0 +1,9 @@
+Feature: A Feature
+
+  Background:
+    Given a thing
+      """json
+      {"this": "is a json doc string",
+      "but": "with a newline in the middle"}
+      """
+

ghokin/transformer.go

@@ -2,6 +2,7 @@ package ghokin
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"os/exec"
 	"regexp"
@@ -85,6 +86,30 @@ func transform(section *section, indent int, aliases aliases) ([]byte, error) {
 			continue
 		}
 
+		if sec.kind == gherkin.TokenTypeDocStringSeparator && len(sec.values) == 1 && sec.values[0].Text == "json" {
+			document = append(
+				document,
+				trimExtraTrailingSpace(indentStrings(paddings[gherkin.TokenTypeOther], []string{`"""json`}))...,
+			)
+
+			var jsonLines string
+			for sec.nex.kind != gherkin.TokenTypeDocStringSeparator {
+				sec = sec.nex
+				for _, value := range sec.values {
+					jsonLines += value.Text
+				}
+			}
+
+			var prettyJSON bytes.Buffer
+			if err := json.Indent(&prettyJSON, []byte(jsonLines), "", "  "); err != nil {
+				return []byte{}, fmt.Errorf("failed to format json: %w", err)
+			}
+
+			document = append(document, trimExtraTrailingSpace(indentStrings(paddings[gherkin.TokenTypeOther], strings.Split(prettyJSON.String(), "\n")))...)
+
+			continue
+		}
+
 		if sec.kind == 0 {
 			continue
 		}

ghokin/transformer_test.go

@@ -410,6 +410,10 @@ func TestTransform(t *testing.T) {
 			"fixtures/file1.feature",
 			"fixtures/file1.feature",
 		},
+		{
+			"fixtures/json.input.feature",
+			"fixtures/json.expected.feature",
+		},
 
 		{
 			"fixtures/cmd.input.feature",