Add .editorconfig file (#6771)

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*.{py,pyi,rst,md,yml,yaml,toml,json}]
+trim_trailing_whitespace = true
+insert_final_newline = true
+indent_style = space
+
+[*.{py,pyi,toml,json}]
+indent_size = 4
+
+[*.{yml,yaml}]
+indent_size = 2