fix redirects plugin for html output

[thautwarm]

Description

redirects plugin not working when --location is specified at the build time, if the location is not a root url.

For example, my blog url is https://thautwarm.github.io/Site-33/ instead of https://thautwarm.github.io/, then the redirection fails to resolve urls.

Related Issues

No issue yet. I found the case by

Check List

• Have you read the
  CODE OF CONDUCT
• Have you read the document
  CONTRIBUTING
  • One pull request per feature. If you want to do more than one thing,
    send multiple pull request.
  • Write tests.
  • Run deno fmt to fix the code format before commit.
  • Document any change in the CHANGELOG.md.

[oscarotero]

Good catch! Thanks for this.
I left a comment to improve your changes.

[thautwarm]

Returning from & to instead of the mixed from & newUrl looks more consistency.

[oscarotero]

Looks great. Thank you!