docs: fix preset layout

[viceice]

Changes:

• add newline after preset json
• declare preset json as json

Context:

• fixes Fix Markdown generation script so output is correct #13348
• Enable syntax highlight renovatebot.github.io#125

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please tick one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[HonkingGoose]

Looks okay to me, just from looking at it.

I would like to know if this actually works before merging it, but I don't think there's a way that's easy enough for me to do myself...

[viceice]

Looks okay to me, just from looking at it.

I would like to know if this actually works before merging it, but I don't think there's a way that's easy enough for me to do myself...

before:

### config:base

Default base configuration for all languages

```
{
  "extends": [
    ":dependencyDashboard",
    ":semanticPrefixFixDepsChoreOthers",
    ":ignoreModulesAndTests",
    ":autodetectPinVersions",
    ":prHourlyLimit2",
    ":prConcurrentLimit10",
    "group:monorepos",
    "group:recommended",
    "workarounds:all"
  ]
}
```
----

### config:js-app

after:

### config:base

Default base configuration for all languages

```json
{
  "extends": [
    ":dependencyDashboard",
    ":semanticPrefixFixDepsChoreOthers",
    ":ignoreModulesAndTests",
    ":autodetectPinVersions",
    ":prHourlyLimit2",
    ":prConcurrentLimit10",
    "group:monorepos",
    "group:recommended",
    "workarounds:all"
  ]
}
```

----

### config:js-app

[HonkingGoose]

That looks a lot better! 🥳

[renovate-release]

🎉 This PR is included in version 31.19.1 🎉

The release is available on:

• GitHub release
• 31.19.1

Your semantic-release bot 📦🚀