Use official AWS packages and allow custom endpoint

[ThinkChaos]

I wanted to use this with a S3 compatible provider, so I made the required changes.
I also took the opportunity to change the AWS API to the official one.

P.S. I follow you on twitter and found this totally randomly, you do lots of cool and interesting things 😃

[tacerus]

Hi! Thanks a lot for this update, as I was trying to use s3server with a custom provider, and only realized after installing it that it was not possible. I cloned your forked repo and built it, and it worked great immediately. It is a real shame that the original developer did not approve your PR yet - I would suggest you go ahead and make your own forked project with it. If you do, please be so nice and remove the Google Tracking code from the HTML template - that's the only thing missing from making this perfect (well, there would be some more ideas from my end, but I'm happy it's working nicely so far). Again - Thank you for this patch, really appreciate it.

[ThinkChaos]

@tacerus thanks for the kind words.
I'm using techknowlogick/caddy-s3browser nowadays. It's not for the exact same use-case as it is more like a standard file browser: it generates one page per directory.

This repo was updated since my PR so if you want to use it I think you should rebase (and remove the tracking if you so desire).