Add a basic editorconfig file

This is mostly useful to avoid people from adding trailing whitespace to
files.

Author: JelteF

.editorconfig

@@ -0,0 +1,17 @@
+# top-most EditorConfig file
+root = true
+
+# basic rules for all files
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+trim_trailing_whitespace = true
+
+[*.{py,js}]
+indent_style = space
+indent_size = 4
+
+[*.html]
+indent_style = space
+indent_size = 1