vim-patch:9.1.1906: filetype: not all Ruby files are recognized (#36526)

Problem:  filetype: not all Ruby files are recognized
Solution: Detect *.rbi and Brewfile as ruby filetype
          (botantony).

- `rbi` is a file extension used by Sorbet, typechecker for Ruby:
   https://sorbet.org/docs/rbi

- `Brewfile` is a bundler file for Homebrew package manager:
   https://docs.brew.sh/Brew-Bundle-and-Brewfile

closes: vim/vim#18697

efc3be77bb

Co-authored-by: botantony <antonsm21@gmail.com>

runtime/lua/vim/filetype.lua

@@ -1099,6 +1099,7 @@ local extension = {
   rjs = 'ruby',
   rxml = 'ruby',
   rb = 'ruby',
+  rbi = 'ruby',
   rant = 'ruby',
   ru = 'ruby',
   rbw = 'ruby',
@@ -1844,6 +1845,7 @@ local filename = {
   ['requirements.in'] = 'requirements',
   ['resolv.conf'] = 'resolv',
   ['robots.txt'] = 'robots',
+  Brewfile = 'ruby',
   Gemfile = 'ruby',
   Puppetfile = 'ruby',
   ['.irbrc'] = 'ruby',