Merge pull request #18185 from clason/vim-8.2.4781

vim-patch:8.2.{4781,4793}: maxima files are not recognized

runtime/lua/vim/filetype.lua

@@ -389,6 +389,12 @@ local extension = {
   mason = "mason",
   master = "master",
   mas = "master",
+  demo = "maxima",
+  dm1 = "maxima",
+  dm2 = "maxima",
+  dm3 = "maxima",
+  dmt = "maxima",
+  wxm = "maxima",
   mel = "mel",
   mf = "mf",
   mgl = "mgl",
@@ -1013,6 +1019,7 @@ local filename = {
   [".mailcap"] = "mailcap",
   ["/etc/man.conf"] = "manconf",
   ["man.config"] = "manconf",
+  ["maxima-init.mac"] = "maxima",
   ["meson.build"] = "meson",
   ["meson_options.txt"] = "meson",
   ["/etc/conf.modules"] = "modconf",