[Bug] Can't change the openapi endpoint url due to hard coding in html

[rocknet]

Describe the bug
Setting OAS_URL_PREFIX to anything other than /docs causes redoc and swagger to fail, because the html looks for /docs/openapi.json (and swagger-config for swagger)

Screenshots

To Reproduce
Initialize Sanic-ext like this:

cfg = Config(oas_ui_default="swagger", oas_url_prefix='/swagger')
Extend(app, config=cfg)

Expected behavior
Swagger UI functions at hostname/swagger

Environment (please complete the following information):

• OS: Windows
• Browser Chrome
• Version 21.9.3 (really pip install -e /main from this repo)

Additional context
This is fixed in a branch in my fork. Let me know if you want a PR. I also fixed / enhanced with the ability to use the root as the openapi endpoint. Tested with redoc and swagger with the default of no prefix set (so default of /docs) and url prefixes ['/docs', '/swagger', '']. I only tested with the base of my installed sanic, which is 21.9.1
rocknet@ec1f277

[ahopkins]

This is fixed in a branch in my fork. Let me know if you want a PR.

Yes please! 😎