vim-patch:9.0.1090: FHIR Shorthand files are not recognized (#21515)

Problem:    FHIR Shorthand files are not recognized.
Solution:   Add a pattern to detect FSH files. (Matthew Gramigna,
            closes vim/vim#11738)

c9207d5d79

Co-authored-by: mgramigna <mgramigna@mitre.org>

runtime/lua/vim/filetype.lua

@@ -419,6 +419,7 @@ local extension = {
   fs = function(path, bufnr)
     return require('vim.filetype.detect').fs(bufnr)
   end,
+  fsh = 'fsh',
   fsi = 'fsharp',
   fsx = 'fsharp',
   fusion = 'fusion',