Allow custom output path for static and external_static instead of only static

[PatryQHyper]

When you set type to external_static and set custom static output_path, it still points to default path in generated HTML.

Generated part of scalar HTML (before PR, output_path is different from public/docs):

<script
    id="api-reference"
    data-url="../docs/openapi.yaml">
</script>

[shalvah]

Good catch!