feat(experimental): allow const for ref sugar declarations

Author: yyx990803

packages/ref-transform/src/refTransform.ts

@@ -217,9 +217,6 @@ export function transformAST(
  statement: VariableDeclaration
  ) {
  excludedIds.add(call.callee as Identifier)
- if (statement.kind !== 'let') {
- error(`${method}() bindings can only be declared with let`, call)
- }
  if (method === TO_VAR_SYMBOL) {
  // $
  // remove macro