Add robots.txt file for better search engine indexing

Author: jedisct1

www/robots.txt

@@ -1,7 +1,8 @@
 User-agent: *
 Allow: /
-Sitemap: https://jedisct1.github.io/draft-denis-ipcrypt/sitemap.xml
 
-# Disallow any potential development or test pages
-Disallow: /dev/
-Disallow: /test/
+# Allow all crawlers to access all content
+Disallow:
+
+# Sitemap location
+Sitemap: https://ipcrypt-std.github.io/sitemap.xml