fix(useExternal): avoid wrong option

[vaakian]

🤔 This is a ...

• New feature
• Bug fix
• Site / documentation update
• Demo update
• TypeScript definition update
• Bundle size optimization
• Performance optimization
• Enhancement feature
• Internationalization
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

💡 Background and solution

Avoid potential wrong option.

For example, if user specifies type: 'js' then css attribute is useless and will be omitted, this PR can help it at type level.

❌ wrong

✅ correct

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

[CLAassistant]

All committers have signed the CLA.

[miracles1919]

我在你的基础上稍微调整了下，看看这样怎么样