Add static file serving with try_files chain ($uri, $uri.html,
$uri/index.html, fallback), regex-based URL rewrites compiled at
startup, response body find/replace for text/html and JS content,
auth subrequests with header capture for path routes, and custom
response headers per route. Extends RouteConfig with static_root,
fallback, rewrites, body_rewrites, and response_headers fields.
Signed-off-by: Sienna Meridian Satterwhite <sienna@sunbeam.pt>