Add-on plugin for s3 compatible storage

[zirconline]

It's clear that a picture bed CMS will be more powerful if it support S3 object storage.

Here is reference list:

https://github.com/aws/aws-sdk-go https://alist.nn.ci/guide/drivers/s3.html#force-path-style https://github.com/libsgh/PanIndex/blob/main/pan/S3.go