Add server-side redirect from root to real content (#1724)

Co-authored-by: RJ Beers <[email protected]>

Author: backport-actions-token[bot]

static/_redirects

@@ -519,3 +519,6 @@ https://0-13-0.docs.pomerium.io/ https://0-13-0.docs.pomerium.com/:splat 301!
 https://0-12-0.docs.pomerium.io/ https://0-12-0.docs.pomerium.com/:splat 301!
 https://0-11-0.docs.pomerium.io/ https://0-11-0.docs.pomerium.com/:splat 301!
 https://0-10-0.docs.pomerium.io/ https://0-10-0.docs.pomerium.com/:splat 301!
+
+# Avoid the index flicker in the browser
+/ /docs