Change the axis color of workflow metrics to match GitHub theme setting

[massongit]

Fix #42

I fix this action to automatically change the axis color of workflow metrics to match GitHub theme setting.

FYI: https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#specifying-the-theme-an-image-is-shown-to

Screenshots

https://github.com/massongit/workflow-telemetry-action/actions/runs/13598930026?pr=1 ( massongit#1 )

Dark mode

Light mode

[massongit]

@rwxdash @suleymanbarman Please review it.

[massongit]

@rwxdash @suleymanbarman @serkan-ozal Please review it.

[BourgoisMickael]

Maybe you can assign them as reviewers to notify them

[massongit]

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/requesting-a-pull-request-review

To assign a reviewer to a pull request, you will need write access to the repository.

I do not have permission to assign reviewers...

[BourgoisMickael]

Can you include a screenshot to show the graphs works well in dark mode

[massongit]

I add screenshots to PR description.

[echoix]

I can confirm it looks the same as the screenshot on GitHub mobile on iOS (from the test PR linked)