Add .editorconfig.

Author: BigBlueHat

.editorconfig

@@ -0,0 +1,13 @@
+# https://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.{cjs,js,json,jsonld,mjs,yaml,yml}]
+indent_style = space
+indent_size = 2