Allow for Pug 3

[vdh]

This has stagnated for quite a while, and even with the latest and greatest Yarn 2 tricks this outdated peer dependency just won't be quiet, despite many years (?) of people using pug 3 without issue just fine.

[JounQin]

@ForbesLindesay Can we merge and release?

[DanTheMan827]

I also would like this.

[webdiscus]

@DanTheMan827
you can try to use modern alternative @webdiscus/pug-loader.
This pug-loader is 100% compatible with original.

Or better use the pug-plugin.
This pug-plugin enable to use the script and style sources directly in Pug.