Add missing github token param

[nuvic]

🗣 Description

Without GITHUB_TOKEN, it hits the rate limit right away:

WARN runtime::init::dataset: The dataset spiceai.issues (github) has been rate limited. GitHub API rate limit exceeded. Try again later, and add a LIMIT clause to your query to reduce the number of requests.

🤔 Concerns

If a new user reading this doesn't have their GITHUB_TOKEN in their .env, it increases the friction to trying out this core feature of spice.ai. An alternative to this example is to use a csv file hosted on github:

  - from: https://raw.githubusercontent.com/LearnDataSci/articles/refs/heads/master/Python%20Pandas%20Tutorial%20A%20Complete%20Introduction%20for%20Beginners/IMDB-Movie-Data.csv
    name: movie_reviews
    acceleration:
      enabled: true
    params:
      file_format: csv
    columns:
      - name: Description
        embeddings:
          - from: remote_service

[lukekim]

Thank you!

[nuvic]

Hello, is there anything else I need to do for it to be merged?