Add general editor config.

Helps with consistency.

.editorconfig

@@ -0,0 +1,11 @@
+root = true
+
+[*]
+indent_style = tab
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+trim_trailing_whitespace = false