feat: Add shell formatters

flake.nix

@@ -135,6 +135,7 @@
           rubyPackages.erb-formatter
           ruff
           shellcheck
+          shfmt
           sqlfluff
           stdenv.cc.cc
           stylelint

lua/plugins/conform-nvim.lua

@@ -9,6 +9,18 @@ return {
         liquid = { 'prettier' },
         nix = { 'alejandra' },
         scss = { 'stylelint' },
+        sh = { 'shellcheck', 'shfmt' },
+      },
+
+      formatters = {
+        shfmt = {
+          prepend_args = {
+            '--indent=2',
+            '--case-indent',
+            '--binary-next-line',
+            '--func-next-line',
+          },
+        },
       },
     },
   },