There is no way to disable strict mode when using cli

Apparently there is no way to disable strict mode when using ajv and that would not be such a big deal unless it would have allowed me to make use of `markdownDescription` property, something that is very popular among schema authors as it allows us to include markdown in descriptions and have nice popup in IDEs, like vscode.

```shell
$ ajv compile -s f/ansible-meta.json
error: strict mode: unknown keyword: "markdownDescription"
```

While I was able to fix the other problems, that one is impossible to address. This also make it impossible to use ajv-cli as part of CI/CD pipelines for validating the schema, as it would always be "invalid" due to this.