Rename the pipeline

[fasterius]

Description of feature

Given the addition of other spatial-based nf-core pipelines it was decided that we should rename this pipeline to something more descriptive, since it will only be dealing with Visium data. While "spatial transcriptomics" is still used interchangeably with "Visium" it would be clearer if the pipeline name reflected the fact that it's only Visium data.

Some proposals from Slack so far:

• visiumflow
• nextvisium
• visiumcore
• visiumpipe
• spatialseq
• spatialflow
• visium

[fasterius]

Completed, new pipeline name is nf-core/spatialvi.