feat(lib): allow emit assets in es mode

[Bigfish8]

Description

#4454

Additional context

This option is for libary mode.
Add emitAssets option to allow user avoid inlining assets.
This only works for es mode and .js file.The css file also inline assets.

By the way, it seems can combine with v-bind for vue to emit assets in css.

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[laizp]

any progress?

[showonne]

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