Support project_folder outside of working directory

[TexKiller]

If the project_folder is specified outside of the current directory, such as with doca init -i ../schemas -o ../documentation, the json schemas paths are messed up, ending up like ../../../schemas/schema.json.

The path to the schemas should be either absolute or relative to the project_folder, and not relative to the working directory.

[handrews]

@TexKiller thanks for filing this. We also want to make doca handle multiple APIs with shared datatype schemas better in general, which involves storing schemas outside of the project directory as well, so that's at least two concerns around this.

[handrews]

This set of packages is being deprecated in favor of the JSON Schema Tools monorepo. Contributions are still welcome here but most work will be done on the new packages.

Note that the new UI is still being designed.

This issue has been filed as cloudflare/json-schema-tools#8