Unable to upload packaged support app that includes TypeScript files

Hello! 

I have a fairly simple sidebar app written in TypeScript (vanilla JS, no frameworks). I'm using Parcel 2 for bundling all assets into a single dist directory, which my manifest.json points to as the sidebar app url. However whenever I package (using ZAT) and upload the app, I receive a "MIME type not supported" error. I'm able to workaround this by removing any TypeScript files that are included in the zipped filed then re-zipping. Then the app loads, however it's missing the javascript. It appears this is because the script type is "module", as I'm able to again work around this by manually updating to "application/javascript". Obviously neither of these workarounds are ideal!

Was wondering if anyone could shed any light as to why this is happening as well as provide some guidance on how to potentially update so that this isn't a manual process.

Extra deets:  The html output from Parcel includes two script tags, one of type module and the other "nomodule" for browsers that don't support. I don't necessarily need to utilize ES modules in production as I'm only using the single JavaScript file.

Thanks!