Description:
This PR adds a concrete example demonstrating the use of next('route') in the “Route handlers” section of the Express routing documentation.

Currently, the docs mention next('route') but don’t show a simple, self-contained example, which could make it unclear for new users. This change:

Adds a GET /user/:id example that uses next('route') to skip to the next matching route.
Includes a short bullet-point explanation of the behavior for two different request paths (/user/5 and /user/0).

Before:
The section explains next('route') but doesn’t show a minimal code sample demonstrating it in action.

After:
The section now contains:

app.get('/user/:id', (req, res, next) => {
  if (req.params.id === '0') {
    return next('route')
  }
  res.send(`User ${req.params.id}`)
})

app.get('/user/:id', (req, res) => {
  res.send('Special handler for user ID 0')
})

In this example:
GET /user/5 → handled by first route → sends "User 5"
GET /user/0 → first route calls next('route'), skipping to the next matching /user/:id route

Why this change improves the docs:

Makes the next('route') behavior obvious without requiring guesswork.
Matches the style and tone of existing Express documentation.
Adds a practical example to complement the textual explanation.