adding 2 new notebooks -- gen ai apps with vertex ai and llama index

[pranavaurora]

No description provided.

[kesmit13]

In the llama notebook, here are some changes:

1. For the API key, we've been using import getpass' and os.environ["OPENAI_API_KEY"] = getpass.getpass("Enter OpenAI API key: ")` to prevent people from committing API keys.

2. Don't set the SINGLESTOREDB_URL, that's already set by the notebook environment.

3. In the SingleStoreReader, I would think we would use 'singlestoredb' for scheme, connection_host for host, connection_port for port, connection_user for user, and connection_password for password.

4. The In[9], In[10], and In[11] don't need print functions, the notebook will print the result.

On the vertex notebook:

1. Remove the SINGLESTOREDB_URL part again.

You'll want to step through both notebooks to make sure they still work.

[pranavaurora]

I removed my 2 notebooks which need quite a lot of changes, and have added the changes to Arnaud's meta.toml file so that gallery won't break

[kesmit13]

I fixed the notebooks myself.