add .editorconfig

.editorconfig

@@ -0,0 +1,30 @@
+[*]
+charset = utf-8
+end_of_line = lf
+indent_style = tab
+indent_size = 4
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.md]
+indent_style = space
+indent_size = 4
+trim_trailing_whitespace = false
+insert_final_newline = false
+
+[*.json]
+indent_style = space
+indent_size = 4
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+# C coding style based on Linux kernel.
+# https://www.kernel.org/doc/html/v5.0/process/coding-style.html
+
+[*.c]
+indent_style = tab
+indent_size = 8
+
+[*.h]
+indent_style = tab
+indent_size = 8