Add seqkit sort to existing seqkit suite

[TomHarrop]

FOR CONTRIBUTOR:

• I have read the CONTRIBUTING.md document and this tool is appropriate for the tools-iuc repo.
• License permits unrestricted use (educational + commercial)
• This PR adds a new tool or tool collection
• This PR updates an existing tool or tool collection
• This PR does something else (explain below)

[bgruening]

I added some tiny changes. Does this still looks good to you @TomHarrop?

The boolean and the select do contain the commanline part in their variable, so we can use them without a check.

[TomHarrop]

Looks good, it failed for me locally when I did that but it passes here so I’m fine with it. Thanks @bgruening