vim-patch:9.1.0593: filetype: Asymptote files are not recognized

Problem:  filetype: Asymptote files are not recognized
Solution: detect '*.asy' files as asy filetype, include
          ftplugin and syntax plugin (AvidSeeker).

Reference: https://asymptote.sourceforge.io/

closes: vim/vim#15252

3088ef094d

Co-authored-by: AvidSeeker <avidseeker7@protonmail.com>

runtime/lua/vim/filetype.lua

@@ -214,6 +214,7 @@ local extension = {
   asn = 'asn',
   asp = detect.asp,
   astro = 'astro',
+  asy = 'asy',
   atl = 'atlas',
   as = 'atlas',
   zed = 'authzed',