vim-patch:9.1.2109: filetype: NetLinx fires are not recognized

Problem:  filetype: NetLinx fires are not recognized
Solution: Detect *.axs and *.axi as netlinx filetype
          (kb).

Reference:
- https://www.amx.com/en/site_elements/amx-language-reference-guide-netlinx-programming-language
- https://kielthecoder.com/2021/06/11/netlinx-getting-started/

closes: vim/vim#19249

6963e3b8bf

Co-authored-by: kb <kim@simple.industries>

runtime/lua/vim/filetype.lua

@@ -848,6 +848,8 @@ local extension = {
   NSP = 'natural',
   NSS = 'natural',
   ncf = 'ncf',
+  axs = 'netlinx',
+  axi = 'netlinx',
   nginx = 'nginx',
   ncl = 'nickel',
   nim = 'nim',