feat: added star history chart

[github-star-history]

Star History chart added, hope you like it! :)

Checks

• I am happy for maintainers to push small adjustments to this PR, to speed up the review cycle
• I have checked that there are no existing pull requests for the same thing

[ellie]

Looks like the API is down - I'd be open to this in theory, but it seems like this might be automated and unreliable

[github-star-history]

@ellie The API has maintained 100% uptime since December 2023. For repositories with a large number of stars, fetching all the data can take some time. To optimize performance, we cache images for 24 hours. When the cache expires, the first request triggers a cache refresh, which takes approximately 40 seconds for this repo. As a result, the first request after the 24-hour period may fail with a timeout error (since github add timeout restrictions and also heroku does). However, this triggers the update process, ensuring that all subsequent requests within the next 24 hours are served in just 2-3 milliseconds.