feat: Add .gitattributes (runatlantis#3244)

.gitattributes

@@ -0,0 +1,11 @@
+# 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.
+*.go text
+*.json text
+*.yml text
+*.yaml text
+*.sh text
+*.tf text