Add memorable command :MDPreview {start,stop}

lua/plugins/utilities.lua

@@ -50,13 +50,41 @@ return {
   {
     'vihu/penview.nvim',
     ft = 'markdown',
+    cmd = 'MDPreview',
     run = function()
       require("penview.build").install()
     end,
     config = function()
-      require('penview').setup({
+      local penview = require('penview')
+      penview.setup({
         browser = 'firefox',
       })
+
+      -- :MDPreview {start,stop} previewing the current file in the browser
+      local commands = { start = 'PenviewStart', stop = 'PenviewStop' }
+      local actions = vim.tbl_keys(commands)
+      table.sort(actions)
+
+      vim.api.nvim_create_user_command('MDPreview', function(opts)
+        local command = commands[opts.args]
+        if not command then
+          vim.api.nvim_echo({
+            {
+              'MDPreview: expected {' .. table.concat(actions, ',') .. '}',
+              "ErrorMsg"
+            }
+          }, true, {})
+          return
+        end
+        vim.cmd(command)
+      end, {
+        nargs = 1,
+        complete = function(lead)
+          return vim.tbl_filter(function(action)
+            return vim.startswith(action, lead)
+          end, actions)
+        end,
+      })
     end,
   },
 }