When `HX-Target` header is present, bypass any configured layout for the
request. This allows a full page reload to render with a layout, i.e.
render the entire page, while a request from htmx will load just the
content directly generated by the view.
Implement `jetzig.http.Request.params()` which parses either a JSON
request body or a query param string into a `jetzig.data.Value`.
Allow configuring params for static site generation - configure an array
of params for each endpoint which is then parsed at build time and a
separate JSON and HTML output is generated for each by invoking the
relevant view function and passing in resource ID/params. Params are
stored in generated `routes.zig` for route matching at run time.
Generate views defined with `request: *jetzig.http.StaticRequest` as
static content into `static/` directory so that exported JSON and HTML
can be rendered direct from disk, skipping runtime rendering.
