Add resources to the deployer

[thibautjombart]

Thinking along the lines of "I'm without internet and I need all the R documentation I can carry with me", it'd be good to add the following to inst/, structured in a simple way, and documented in the inst/README:

• Rstudio's cheatsheets
• some templates of Rmardown reports (sitreps etc)
• some templates of shiny apps
• an offline version of RECON learn, when this becomes possible

This will be an ongoing process; for the time being cheatsheets would be great. @zkamvar could you give this a first pass?