Add redirect generator to make Netlify's CDN redirect to the right places.

Netlify will redirect with a 301 status to the right places without the
need of a custom javascript file.

The current redirects.js is not removed so production can keep working
as it is for now.

Signed-off-by: David Calavera <david.calavera@gmail.com>

netlify.toml

@@ -1,6 +1,6 @@
 [build]
-  command = "make build"
+  command = "make build generate-redirects"
   publish = "_site"
 
 [context.deploy-preview]
-  command = "make build-preview"
+  command = "make build-preview generate-redirects"