master redirect (#126)

Author: jordan-smith721

config/redirects

@@ -7,6 +7,7 @@ symlink: upcoming -> master
 
 raw: ${prefix}/ -> ${base}/current/
 raw: ${prefix}/stable -> ${base}/current/
+raw: ${prefix}/master -> ${base}/upcoming/
 
 # Redirects for standardized (new) page URLs in old docs
 [*-v8.1]: ${prefix}/${version}/compatibility/ -> ${base}/${version}/reference/compatibility/