tools/code-formatting: Add EditorConfig file

EditorConfig helps maintain consistent coding styles for multiple developers
working on the same project across various editors and IDEs:
https://editorconfig.org/

Signed-off-by: José Expósito <jose.exposito89@gmail.com>

.editorconfig

@@ -0,0 +1,11 @@
+# https://editorconfig.org/
+
+root = true
+
+[*.{c,h}]
+charset = utf-8
+end_of_line = lf
+indent_size = 8
+indent_style = tab
+insert_final_newline = true
+trim_trailing_whitespace = true