feat: implementing cleaner handling of JSON in cURL snippets

[erunion]

This is a reworking of my original PR in #219 for this, just against the new TS rewrite.

This slightly modifies the cURL snippet target to clean up how it handles JSON payloads into rendering them on multiple lines.

This is what they currently look like:

curl --request POST \
  --url http://mockbin.com/har \
  --header 'content-type: application/json' \
  --data '{"number":1,"string":"f\"oo","arr":[1,2,3],"nested":{"a":"b"},"arr_mix":[1,"a",{"arr_mix_nested":{}}],"boolean":false}'

With this change:

curl --request POST \
  --url http://mockbin.com/har \
  --header 'content-type: application/json' \
  --data '
{
  "number": 1,
  "string": "f\"oo",
  "arr": [
    1,
    2,
    3
  ],
  "nested": {
    "a": "b"
  },
  "arr_mix": [
    1,
    "a",
    {
      "arr_mix_nested": {}
    }
  ],
  "boolean": false
}
'

🐳 Things to note

• I don't love how arrays and objects get blown out if they're small enough to be able to fit on a single line (like arr is above), but the stringify-object library that's used throughout this library for doing prettification of objects removes quotes from object keys, which in this case would result in invalid JSON from being sent.
• If the JSON payload has a ' quote within it, we can't wrap that in a --data string without busting STDIN so instead we wrap the JSON within a HEREDOC:

curl --request POST \
  --url http://mockbin.com/har \
  --header 'content-type: application/json' \
  --data @- <<EOF
{
  "number": 1,
  "string": "f'oo"
}
EOF

• To prevent miniscule JSON payloads from getting blown out snippets, if the stringified JSON is less than or equal to 20 characters we'll render it on one line:

curl --request POST \
  --url http://mockbin.com/har \
  --header 'content-type: application/json' \
  --data '{"foo":null}'

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