Add .gitattribute to define line endings

.gitattributes

@@ -0,0 +1,14 @@
+# Set the default behavior, in case people don't have core.autocrlf set.
+* text=auto
+
+# Explicitly declare text files you want to always be normalized and converted
+# to native line endings on checkout.
+*.r text
+*.Rmd text
+*.md text
+*.json text
+
+# Denote all files that are truly binary and should not be modified.
+*.png binary
+*.jpg binary
+*.rda binary