Feature: Add examples as Tutorials or How-To Guides

Bazel examples live in a few places, such as

- https://github.com/aspect-build/bazel-examples
- https://github.com/bazelbuild/examples/
- https://awesomebazel.com/#demos
- Lots of smaller one-offs

We should make it easy for anyone to send us a trivial PR, to a .json file or something, to add their examples to the docsite.

The index of examples should be easy enough to search and browse, so that even after we've accumulated hundreds of them, users are still able to find one that is similar to their use case (if it exists)

No implementation files or tests are named. Start by inspecting the existing docsite structure and the example sources at aspect-build/bazel-examples, bazelbuild/examples, and awesomebazel.com/#demos. Done should include a contribution path for trivial example submissions and an index that remains searchable and browsable as examples grow.

Written by the indexing model from the issue text.