feat: add attrs option

[fengzilong]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

related issue: #413

support customizing attributes for link tag

Breaking Changes

No

Additional Info

[jsf-clabot]

All committers have signed the CLA.

[fengzilong]

Any review please?

[alexander-akait]

Remove yarn.lock, also it think it should be done using hooks, it is allow other plugins change attributes

[fengzilong]

Thanks for reply, I'll look into the hooks implementation

[dutzi]

Any updates regarding this PR?

Our use case: we're using css-vars-ponyfill for IE11, we are a widget embedded in a website, we want css-vars-ponyfill to run only on CSS generated by us.

[alexander-akait]

Please add tests

[dutzi]

Hey @evilebottnawi, I tried looking at the test/cases directory for reference as to how I can write a test for such feature, but I couldn't find anything that resembles this setup. In this test we are required to test for the code generated by this block, but what file does it output? What would I put in the expected folder

Can you please provide some guidance?

[alexander-akait]

Close in favor #445