Add content-type to assets uploaded to s3

[stalgiag]

I have verified that this pull request:

• has no linting errors (npm run lint)
• is from a uniquely-named feature branch and has been rebased on top of the latest master. (If I was asked to make more changes, I have made sure to rebase onto master then too)
• is descriptively named and links to an issue number, i.e. Fixes #123

resolves #496
addresses #1196

This adds the relevant Content-Type metadata to files uploaded to AWS. This fixes a bug introduced with p5 v0.10.2 which checks the header's content-type to determine whether an asset is a GIF.

I have tested this locally with a personal S3 bucket.

Potential issues - I think this only handles assets uploaded through the drag+drop interface. I assume that this is the only way that a user will upload a media asset but I could be wrong.

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[catarak]

yay thank you!

eventually, it will be possible to upload assets via the api (#542), but that can be handled separately from this PR.

[catarak]

one major issue is that all of the assets currently uploaded to S3 don't have a content type, so we'll need to write a script to update them. i'm looking at https://stackoverflow.com/questions/41015200/how-to-change-content-type-of-amazon-s3-objects

EDIT: however, since old sketches will still be using older versions of p5.js, maybe it's fine to just leave it.

[catarak]

anyway, this is working great for me and i'm going to merge it.

[stalgiag]

Oh yeah! I didn't think about that. Perhaps this will be an edge-case? Updating the version on existing projects seems rare, but I may be missing something. If writing a script to update the existing assets proves difficult, then we could add something on the p5 side to catch this and at least output a helpful warning.

[catarak]

i imagine that folks will rarely update the p5.js version in existing sketches, so yeah, i think it's more of an edge case. it would be cool if p5.js could throw out a useful warning if possible!

[stalgiag]

I agree! Opened a PR on the p5 library side :-)