Add Portable Verison

[3geETR]

A portable version like the one in Prism Launcher would be great. All the files, instances etc. is saved in that folder.

[Th0rgal]

PR #43 adds shard account export and shard account import commands that allow exporting/importing accounts with tokens to a portable JSON file. This partially addresses the portability concern for accounts.

For a full portable version (storing instances, mods, etc. in a single folder), that would require additional work on the profile/instance storage system.