Create a frontend webpage for summarization feature

With #17 in place, it would be nice to have a front-end in place.

The only thing necessary on this page is a textbox for the slug and a button `Summarize`, along with an area where the summary can be shown.
It would also be nice to have the slug filled via a querystring parameter.

This could be a static website, invoking the `/summarize/{slug}`-endpoint.
The site will be hosted on a subdomain: https://summarize.[url].[extension]/
The querystring parameter will be called `slug` to keep the term consistent across the solution.

Start by reviewing the existing Azure/Bicep setup and the `/summarize/{slug}` endpoint from issue #17. Create a static page with a slug textbox, a `Summarize` button, and a summary display, using the `slug` query parameter to prefill the textbox. Done means the page invokes the endpoint and can be hosted at the proposed subdomain.

Written by the indexing model from the issue text.