Documentation & R-CMD Check Workflows, Remove rgpt, check .Rprofile & check NEWS

[jan-abel-inwt]

• [x] https://github.com/Pandora-IsoMemo/docs/issues/12
• [x] https://github.com/Pandora-IsoMemo/docs/issues/11
• [x] https://github.com/Pandora-IsoMemo/drat/issues/35
• [x] https://github.com/Pandora-IsoMemo/drat/issues/34