Updated EditorConfig (#4394)

* Set character set to UTF-8 for all files.
* Use tabs in C related files.

.editorconfig

@@ -6,9 +6,15 @@ root = true
 
 # Add a blank newline to the end of every file after saving
 # Trim trailing whitespace
+# Adjust character set
 [*]
 insert_final_newline = true
 trim_trailing_whitespace = true
+charset = utf-8
+
+# Use tabs in source
+[*.{cpp,c,hpp,h}]
+indent_style = tab
 
 # YAML does not support hard tabs.
 [*.{yml,yaml}]