Fix /login and /signup to serve actual content instead of redirects

- Change /login from 301 redirect to direct serve of index.html
- Change /signup to explicitly serve signup.html file

Author: Arpith Siromoney

static/_redirects

@@ -15,8 +15,8 @@
 /*.txt /:splat.txt 200
 
 # Folder redirects - preserve existing links
-/login /login/ 301
-/signup /signup 200
+/login /login/index.html 200
+/signup /signup.html 200
 /help /help/ 301
 /welcome /welcome/ 301
 /settings /settings/ 301