Let Hugo resize the Post Preview Image in Overviews

[sethiele]

For a smaller Post Preview Image I changed the way of adding it to the post_overwiew.
It use the Hugo Resize function to fit it to the max size of image withe.
Therefore the Image have to be stored in the post folder with *_header.{png,jpg}as name.

The old way with the page variable will also work, but without resizing.

[ibnunowshad]

I am getting below error in my Gitlab ci

Checking out 00c6a670 as master...

Updating/initializing submodules recursively...
Executing "step_script" stage of the job script
$ hugo
Total in 28 ms
Error: add site dependencies: load resources: loading templates: "/builds/website/www-example-com/layouts/partials/post_preview.html:49:1": parse failed: template: partials/post_preview.html:49: unexpected EOF
ERROR: Job failed: exit code 1```