chore(.editorconfig): add .editorconfig file

Closes angular#8278

Author: treyhunner

.editorconfig

@@ -0,0 +1,21 @@
+# http://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 2
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[src/ngLocale/**]
+insert_final_newline = false
+
+[dropdown-toggle.js]
+trim_trailing_whitespace = false
+insert_final_newline = false
+
+[htmlparser.js]
+insert_final_newline = false