Incorrect rest pose

Hello,
Thanks for this great exporter!
I've noticed one issue: it does not export the right bind pose/rest pose when the animations are not in rest pose on the first frame. Instead, the pose at the first frame is set as the bind pose. Is this a known issue of this exporter, or am I missing something?
By the way, i've updated the code to Blender 2.8, in case you're interested i'll submit a pull request.

Start by reproducing the export in Blender with an animation whose first frame is not the rest pose. Then inspect the exporter path that writes the bind or rest pose. Done means the exported Collada file preserves the actual rest pose instead of using the first animation frame; the issue mentions no specific file or test to run.

Written by the indexing model from the issue text.