vim-patch:9.1.0873: filetype: Vivado files are not recognized

Problem:  filetype: Vivado files are not recognized
Solution: detect '*.mss' files as 'mss' filetype
          (Wu, Zhenyu)

references:
https://docs.amd.com/r/2020.2-English/ug1400-vitis-embedded/Microprocessor-Software-Specification-MSS

closes: vim/vim#15907

a87462a498

Co-authored-by: Wu, Zhenyu <wuzhenyu@ustc.edu>

runtime/lua/vim/filetype.lua

@@ -792,6 +792,7 @@ local extension = {
   mof = 'msidl',
   odl = 'msidl',
   msql = 'msql',
+  mss = 'mss',
   mu = 'mupad',
   mush = 'mush',
   mustache = 'mustache',