fix TrailingSlashIntegration

Trailing slash handling was not working correctly on the redirect page.
In case of redirection, the component parameter of astro:build:done is passed
the value of the redirection config as is, so it should be handle the same as
for "index" cases when it ends with a slash.

src/lib/TrailingSlashIntegration.ts

@@ -12,7 +12,7 @@ export default function trailingSlash(): AstroIntegration {
           dedupe(routes)
             .filter(
               ({ component, pathname }) =>
-                parse(component).name !== "index" && pathname !== "/404"
+                (parse(component).name !== "index" || component.endsWith("/")) && pathname !== "/404"
             )
             .map(async ({ pathname }) => {
               if (!pathname) return;