Please update get_R.R code to work with R versions 4 and above

The following two lines in get_R.R code should be updated to prevent errors while creating apps of versions >=4:

latest_R_version <- readLines("https://cran.rstudio.com/bin/windows/base/", warn = F) %>%
stringr::str_extract("[1-3]\\.[0-9]+\\.[0-9]+") %>% stats::na.omit() %>% unique()

old_R_versions <- readLines("https://cran.rstudio.com/bin/windows/base/old/", warn = F) %>%
stringr::str_extract("[1-3]\\.[0-9]+\\.[0-9]+") %>% stats::na.omit()

Lines 2 and 4 should be replaced with [1-4] to apply for versions 4 and above that will be released in the future. Else, the Create_app function will throw an error

Check the code below for example: