Latest Zmpl provides `template.renderWithLayout(other_template, data)`,
allowing a template to be renedered within another template.
Create layouts in `src/app/views/layouts/` or use
`jetzig generate layout [name]` and set `pub const layout = "name";` in
each view file.
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.
