Ensure LF on checkouts and in editors (#9259)

This will ensure our repo is always checked out with LF line endings
which should help Windows users who have line ending normalization
enabled.

Additionally, added the LF preference to .editorconfig.

.editorconfig

@@ -5,6 +5,7 @@ root = true
 charset = utf-8
 insert_final_newline = true
 trim_trailing_whitespace = true
+end_of_line = lf
 
 [*.go]
 indent_style = tab