Problem loading images to gitlab with `_` in the name

[shortcipher3]

I was debugging a problem I found with images not showing up in gitlab when using cml comment create and found some strange things, here is my test set:

    - echo "# no changes" > report.md
    - echo "![atest](./reports/model_pr_curves/person_iou0.5_51.png)" >> report.md
    - cp ./reports/model_pr_curves/person_iou0.5_51.png test.png
    - echo "# local_no_special_chars" >> report.md
    - echo "![btest](./test.png)" >> report.md
    - cp ./reports/model_pr_curves/person_iou0.5_51.png ./reports/model_pr_curves/test.png
    - echo "# nested_no_special_chars" >> report.md
    - echo "![ctest](./reports/model_pr_curves/test.png)" >> report.md
    - cp ./reports/model_pr_curves/person_iou0.5_51.png ./d_._test.png
    - echo "# local_special_chars" >> report.md
    - echo "![dtest](./d_._test.png)" >> report.md
    - cp ./reports/model_pr_curves/person_iou0.5_51.png ./reports/model_pr_curves/aaaaaaaaaaaaaaaa.png
    - echo "# long_path" >> report.md
    - echo "![etest](./reports/model_pr_curves/aaaaaaaaaaaaaaaa.png)" >> report.md
    - echo "![image](wild/creative/thinking/exercise.png)" >> report.md
    - npx github:iterative/cml#warn-publish-enoent comment create --publish-native report.md

no changes (atest) fails to load, local_no_special_chars (btest) loads,  nested_no_special_chars (ctest) loads, local_special_chars (dtest) fails to load, and long_path (etest) loads

It appears that cml doesn't like the _ character in the name. Also I noticed that on a different run the long_path test failed to load, I wonder if the content in the square brackets needs to be unique?