chore(ci): run tests on many versions of nvim

.github/workflows/tests.yml

@@ -6,6 +6,16 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
+        nvim_version:
+          - nightly
+          - v0.7.0
+          - v0.7.2
+          - v0.8.0
+          - v0.8.1
+          - v0.8.2
+          - v0.8.3
+          - v0.9.0
+          - v0.9.1
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3
@@ -13,7 +23,7 @@ jobs:
         shell: bash
         run: |
           mkdir -p /tmp/nvim
-          wget -q https://github.com/neovim/neovim/releases/download/nightly/nvim.appimage -O /tmp/nvim/nvim.appimage
+          wget -q https://github.com/neovim/neovim/releases/download/${{ matrix.nvim_version }}/nvim.appimage -O /tmp/nvim/nvim.appimage
           cd /tmp/nvim
           chmod a+x ./nvim.appimage
           ./nvim.appimage --appimage-extract