Add dynamic import attributes

[029A-h]

According to this: tc39/ecma262#3057 (comment) we are, or very soon will be, at stage 4 with dynamic import attributes.

Dynamic import attributes are still in pending status due to stage 3 (#1111).

Can we now include this feature in Acorn as well?

Motivation
The Node REPL does not support direct dynamic import with await.

> await import('/tmp/data.json', { with: { type: 'json' } });
Uncaught SyntaxError: 
await import('/tmp/data.json', { with: { type: 'json' } })
                                                 ^

Unexpected token ','

This unwanted behavior is caused by Acorn's lack of support for dynamic import attributes (nodejs/node#47463).

[marijnh]

You can prepare a pull request, but we don't merge features until they hit stage 4.

[ota-meshi]

I believe Acorn already supports dynamic import attributes.

acorn/test/tests-import-attributes.js

Line 373 in 3c6a5a9

'import("foo.json", { with: { type: "json" } });',

[marijnh]

Oh, indeed, they are actually already in acorn 8.14.0