Offer tour through app which includes data uploads and first steps

[alex-d13]

• https://github.com/carlganz/rintrojs
• https://github.com/iSEE/iSEE/blob/master/R/defaultTour.R
• https://github.com/omnideconv/DeconvExplorer/blob/3435b42dc9f7906be6148894c4aaa40b6cc24f63/R/DeconvExplorer.R#L711
• https://github.com/omnideconv/DeconvExplorer/blob/master/R/IntroTour.R