Add .editorconfig

.editorconfig

@@ -0,0 +1,20 @@
+# EditorConfig: https://editorconfig.org/
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 4
+indent_style = space
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.mk]
+indent_style = tab
+
+[Makefile]
+indent_style = tab