refactor: update .gitignore

Author: salim-b

.gitignore

@@ -8,9 +8,14 @@ Thumbs.db
 # R(Studio)-specific (temp) files
 .Rapp.history
 .RData
+.RDataTmp
 .Rhistory
 .Rproj.user
 .Ruserdata
 
-# API keys
+# generated vignette output
+vignettes/*.html
+vignettes/*.pdf
+
+# API credentials/tokens
 .httr-oauth