fix: babel-types: ImportDeclaration: add assertions

[coderaiser]

Q	A
Fixed Issues?	Fixes #12262
Patch: Bug Fix?	Yes
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

When using template.ast with code:

import json from "./foo.json" assert { type: "json" };

Resulting AST contains no assertions field. This PR fixes this.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/31190/

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Sandbox	Source
babel-repl-custom-plugin	Configuration
babel-plugin-multi-config	Configuration
babel-repl-custom-plugin	Issue #12262

[nicolo-ribaudo]

Thanks! Can you also add this to export declarations? (faaebfe)

[coderaiser]

@nicolo-ribaudo Sure, done in c2918df.

[nicolo-ribaudo]

Thanks!

[existentialism]

@coderaiser thanks!