Added volunteer resources.
The 'getting started' and 'reference guide PDFs come from the old (1.4) support area of the scratch site: http://info.scratch.mit.edu/es/Support
The scratch cards come from the page linked to in that same page; note that the Desliza card links to the English version (05_glide_v14.pdf), and that the Broadcast and Timer cards are missing in Spanish (I've taken English versions of them from user tuktu's fork, not sure where he got them from).