Do not add style as body link if it already exists

[kurtinge]

When a stylesheet link already exists in the head and preload is supported the stylesheet is added twice.

This is also mentioned in https://github.com/faceyspacey/extract-css-chunks-webpack-plugin/pull/300#issuecomment-752047229

This PR prevent the link from being added to the body if it already is loaded.

[t1mwillis]

@ScriptedAlchemy can we get this merged in and released?

Lighthouse penalizes this fairly heavily:

[SuperOleg39]

@ScriptedAlchemy, big request, merge and publish the fix, if you will have at least a little time

[shinelp100]

ooh man thx!

[iPrytz]

I have tested this and it is working well. The problem I had was because I hadn't set the publicPath in for the build, but now it works!

[luizotcarvalho]

I can confirm that this PR fix the problem, but at this point I don't expect to be merged any time soon, my solution was to use patch-package to apply the fix direct to the node_modules/extract-css-chunks-webpack-plugin/dist/index.js file

If you are using [email protected] just create this file on the patches folder and follow the "Set-up" instruction on patch-package page.

[ScriptedAlchemy]

Sorry <3 its been a while hehe

[ScriptedAlchemy]

released