docs: add jsonschema

[ldez]

Edit: Superseded by #4488

---

• copy the JSON schema from https://github.com/SchemaStore/schemastore/blob/master/src/schemas/json/golangci-lint.json
• add the next JSON schema (v1.57.0)

The schema will be published here:

• https://raw.githubusercontent.com/golangci/golangci-lint/master/jsonschema/golangci.jsonschema.json
• https://raw.githubusercontent.com/golangci/golangci-lint/master/jsonschema/golangci.next.jsonschema.json
• https://raw.githubusercontent.com/golangci/golangci-lint/master/jsonschema/custom-gcl.jsonschema.json

When this PR is merged, I will create a PR on the schema store to reference our schema.

Fixes #4486
Fixes #1453

[bombsimon]

🎉

[ldez]

Sorry, I moved the schema after your review: the files were too deep in the tree, and I think will forget them.
I think we don't need to publish them on the domain golangci-lint.run.

[ldez]

I renamed the files to follow the same name as the config file names.