feat(downstream): check client capability before formatting

modules/lsp/lsp.nix

@@ -204,10 +204,12 @@ in {
             buffer = bufnr,
             callback = function()
               if vim.g.formatsave then
+                if client.supports_method("textDocument/formatting") then
                   local params = require'vim.lsp.util'.make_formatting_params({})
                   client.request('textDocument/formatting', params, nil, bufnr)
                 end
               end
+            end
           })
         end