Add a .editorconfig with our chosen formatting options.

Author: chrisgavin

.editorconfig

@@ -0,0 +1,10 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.ts]
+indent_style = space
+indent_size = 2