[Docs]: V6 - Mixing up <Route /> with lists [<Route />, <Route />] within one <Routes /> looks working but isn't mentioned in the docs and covered in unit tests.

[chi11ed]

Describe what's incorrect/missing in the documentation

Hi!

Just noticed that sometimes in the legacy projects entire batches of routes are stored as arrays.

So when migrating from v5 to v6 there can be unclear working situation when one can do something like this:

      <Routes>
        <Route path="/" element={<Layout />}>
          <Route index element={<Home />} />
          {[
            <Route
              path="about"
              element={
                <React.Suspense fallback={<>...</>}>
                  <About />
                </React.Suspense>
              }
            />,
            <Route
              path="dashboard/*"
              element={
                <React.Suspense fallback={<>...</>}>
                  <Dashboard />
                </React.Suspense>
              }
            />,
          ]}
          <Route path="*" element={<NoMatch />} />
        </Route>
      </Routes>

Despite there is error output regarding missing keys - it seems to be silently working, but

1. It's not documented
2. Unit tests contain only test for Fragment

Could you please add some for better clarity around arrays usages? Maybe worth to mention that those are expected to be flattened.

[timdorr]

This isn't a supported way of building route trees, so we're not going to document it. It may happen to work, but that's not intentional.