Add .editorconfig internally

Summary: This file is causing problems with ShipIt because it exists externally on the s2s-release branch but not on the internal version.

Reviewed By: HeyMultiverse

Differential Revision: D22652162

fbshipit-source-id: dd707765

.editorconfig

@@ -0,0 +1,25 @@
+# This file is for unifying the coding style for different editors and IDEs
+# editorconfig.org
+
+# WordPress Coding Standards
+# https://make.wordpress.org/core/handbook/coding-standards/
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = tab
+
+[{.jshintrc,*.json,*.yml,*.env}]
+indent_style = space
+indent_size = 2
+insert_final_newline = false
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.txt]
+end_of_line = crlf