Have 'mfdoc' open the local site when it's ready

buildroot/share/git/mfdoc

 
 echo "Previewing MarlinDocumentation..."
 
-# wait to open the url for about 8s
-( sleep 45; opensite ) &
-
-bundle exec jekyll serve --watch --incremental
+bundle exec jekyll serve --watch --incremental | {
+  while IFS= read -r line
+  do
+    [[ $line =~ "Server running" ]] && opensite
+    echo "$line"
+  done
+}