Add plot alpha diversity

[paulzierep]

We love that tool and currently plan to develop a series of use-case based tutorials using Galaxy. See https://github.com/usegalaxy-eu/project-ideas/issues/41 We will probably also work on using the shiny app as an interactive tool in Galaxy. I really like the plot alpha diversity option, but it does not exist as individual function. Could you maybe add it to the tool stack form here https://github.com/KasperSkytte/Amplicon-visualiser/blob/ba8acbc39868119c63f49dccb3ec12c5b667c759/sourcefiles/plot_sv.R#L72-L149