Get hosted files as byte array

[dwight9339]

Fixes #2075

Changes: Specify response type "arraybuffer" when fetching external project files for download.

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• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

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• p5.js-web-editor

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