Support embedded directories

[ventsislav-georgiev]

Describe the feature

There is a new feature in Golang 1.16 which allows embedding multiple files in the executable.
More info: https://blog.jetbrains.com/go/2021/06/09/how-to-use-go-embed-in-go-1-16

Will be great if configor has a LoadFromMemory method that allows passing embed.FS to it instead of a file path.

Motivation

The embedding of config files is useful when the executable cannot use absolute paths to refer to its config files and relative paths depend on the working directory which causes issues.