feat: support for multiple inlined stylesheets in the same style tag

[wille]

This PR contains a:

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

Motivation / Use-Case

I have multiple CSS chunks in my web application and in some cases I want to inline more than one of these chunks into a single <style> tag.

Currently data-href does only support one href so I would have to create one style tag per chunk that is inlined which is not super convenient in my current stack.

<style data-href="/static/test.css,static/test2.css">

Breaking Changes

Additional Info

[jsf-clabot]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #586 (b28c5b8) into master (1565706) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #586   +/-   ##
=======================================
  Coverage   91.16%   91.16%           
=======================================
  Files           9        9           
  Lines         543      543           
  Branches      145      145           
=======================================
  Hits          495      495           
  Misses         44       44           
  Partials        4        4           

Impacted Files	Coverage Δ
src/index.js	90.04% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 1565706...b28c5b8. Read the comment docs.

[alexander-akait]

Sorry, it is not valid

[lsycxyj]

I suppose maybe you should do this by html plugin