fix: Set proper image target link in template

[corentinbettiol]

We saw that even when selecting the "open in a new window" (or tab) option, the template was not displaying the target="_blank" attribute in the link of an image plugin.

That's because the template is using instance.link_target instead of instance.target, so I fixed that in the template :)

[codecov[bot]]

Codecov Report

Merging #146 (733661c) into master (b4e8536) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #146   +/-   ##
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  Coverage   86.81%   86.81%           
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  Files         119      119           
  Lines        3087     3087           
  Branches      329      329           
=======================================
  Hits         2680     2680           
  Misses        300      300           
  Partials      107      107           

[fsbraun]

@corentinbettiol Well spotted! Can you also update the change log?

[corentinbettiol]

@fsbraun Sure, is this okay?