feat: import ts with .js in vue

[bluwy]

Description

Fix #6671

Support importing .ts files via .js. Added a new meta.vite.lang flag to provide the hint.

Additional context

Initially instead of .lang I used .isTs, maybe that's desirable?

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[shir0u]

Very nice, hope this gets merged and released soon 👍

[haoqunjiang]

Looks good to me!