Add a .editorconfig

Fixes #179

.editorconfig

@@ -0,0 +1,17 @@
+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.{js,rs,css,tera}]
+charset = utf-8
+
+[*.{rs,tera,css}]
+indent_style = space
+indent_size = 4
+
+[*.js]
+indent_style = space
+indent_size = 2