Fix $schema key not allowed in config json schema

[dbtek]

Fixes json schema validation to allow $schema key which provides ide support.

Related issue(s)

#1082

Checklist

• [x] I have read the contributing guidelines.
• [x] I have referenced an issue containing the design document if my change introduces a new feature.
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• [ ] I have added tests that prove my fix is effective or that my feature works.
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[dbtek]

Thanks @zepatrik. Sorry I couldn't reply in time.

[vinckr]

Hello @dbtek Congrats on merging your first PR in Ory 🎉 ! Your contribution will soon be helping secure millions of identities around the globe 🌏. As a small token of appreciation we send all our first time contributors a gift package to welcome them to the community. Please drop me an email and I will forward you the form to claim your Ory swag!