Add health check support

lua/gh_dash/health.lua

@@ -0,0 +1,37 @@
+local M = {}
+
+--- Called by :checkhealth gh_dash
+function M.check()
+  vim.health.start 'gh-dash.nvim'
+
+  if vim.fn.has 'nvim-0.10' == 1 then
+    vim.health.ok 'Neovim >= 0.10'
+  else
+    vim.health.warn 'Neovim 0.10+ is recommended for full feature support'
+  end
+
+  if vim.fn.executable 'gh' == 1 then
+    vim.health.ok '`gh` CLI found'
+  else
+    vim.health.error('`gh` CLI not found', {
+      'Install from https://cli.github.com/',
+      'e.g. `brew install gh` on macOS',
+    })
+  end
+
+  local handle = io.popen 'gh extension list 2>/dev/null'
+  if handle then
+    local output = handle:read '*a'
+    handle:close()
+    if output and output:find 'gh%-dash' then
+      vim.health.ok '`gh-dash` extension installed'
+    else
+      vim.health.warn('`gh-dash` extension not found', {
+        'Install with: `gh extension install dlvhdr/gh-dash`',
+        'Or set `autoinstall = true` in your plugin config.',
+      })
+    end
+  end
+end
+
+return M