Add new test facility leveraging latest Vader

.github/workflows/ci.yml

@@ -9,3 +9,15 @@ jobs:
       - name: Run tests
         run: cd test && ./run-tests
         shell: bash
+  test-new:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Vim
+        run: sudo apt-get install vim
+
+      - name: Test
+        run: |
+          git clone https://github.com/junegunn/vader.vim.git
+          vim -Es -Nu ./test/new-vimrc -c 'Vader! test/*'

test/new-vimrc

@@ -0,0 +1,17 @@
+set rtp+=vader.vim
+set rtp+=.
+
+filetype plugin indent on
+syntax on
+
+set nocompatible
+set tabstop=8
+set softtabstop=4
+set shiftwidth=4
+set expandtab
+set backspace=2
+set nofoldenable
+set foldmethod=syntax
+set foldlevelstart=10
+set foldnestmax=10
+set ttimeoutlen=0