Where does this feature request/fix of filtering when uploading files belong?

Using a R-shiny app in Ubuntu, with a field to upload an .Rmd file, that has a filter for file extension:

# R-shiny code
fileInput("id",
  "label",
  accept = c(
    ".Rmd" # this fails the same way as: ".Rmd", ".rmd", ".RMD" 
  )
)

# html produced by R

Ubuntu's Chrome file selector shows only: .rmd, and .RMD files in the file selector window. In Windows this problem does not happen for obvious reasons. In Mac Chrome, the problem does not happen .Rmd is the common way to write that extension, so, it would be desirable to show those files when filtering. This seems to depend on mimetypes, or nautilus (Gnome) Looking in https://mimetype.io/all-types , R-markdown, .Rmd is not defined. So, I wonder what could be a next step to allow linux to show/filter .Rmd files, in addition to .rmd and .RMD when uploading files to a site