Add atom sort function in the order of positions to make NEB preparation easier

[Ionizing]

Sorting algorithms implemented in ionizing@e0897e56ea33111ddef940937214a3ab3328a214 .. ionizing@71d1a28e34c33dd77ada2322edfbd1b9a43641fc .

[Ionizing]

However,

• [ ] the frontend needs to be refined to be divided into multiple subcommands.