Add zimg

[sshockwave]

Checklist

• Title of this PR is meaningful: e.g. "Adding my_nifty_package", not "updated meta.yaml".
• License file is packaged (see here for an example).
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[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/zimg) and found it was in an excellent condition.

[sshockwave]

Ready to go!

@conda-forge-admin, please ping conda-forge/help-c-cpp

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-webservice.

I was asked to ping @conda-forge/help-c-cpp and so here I am doing that.