build(docs-infra): add a tool to create new examples (#39283)

This tool can be run from anywhere in the aio folder as:

```sh
yarn create-example <example-name>
```

It will create some basic scaffold files to get the example started.
After creation the developer should then use `yarn boilerplate:add`
or similar to ensure that the example can be run and tested.

You can optionally provide an absolute path to a pre-existing CLI
project and it will copy over appropriate files (ignoring boilerplate)
to the newly created example.

```sh
yarn create-example <example-name> /path/to/other/cli/project
```

Fixes #39275

PR Close #39283

aio/content/examples/.gitignore

@@ -32,6 +32,8 @@
 **/karma-test-shim.js
 **/browser-test-shim.js
 **/node_modules
+**/yarn.lock
+**/package-lock.json
 
 # built files
 *.map