vim-patch:9.1.0926: filetype: Pixi lock files are not recognized

Problem:  filetype: Pixi lock files are not recognized
Solution: detect "pixi.lock" file as yaml filetype
          (Brandon Maier)

Reference:
https://pixi.sh/latest/features/lockfile/

closes: vim/vim#16212

7d1bb90dcf

Co-authored-by: Brandon Maier <brandon.maier@gmail.com>

runtime/lua/vim/filetype.lua

@@ -1874,6 +1874,7 @@ local filename = {
   ['.clangd'] = 'yaml',
   ['.clang-format'] = 'yaml',
   ['.clang-tidy'] = 'yaml',
+  ['pixi.lock'] = 'yaml',
   ['yarn.lock'] = 'yaml',
   matplotlibrc = 'yaml',
   ['.condarc'] = 'yaml',