Fix #501: Use absolute URL for STScI logo in README

[karlhillx]

The relative-path img tag (docs/_static/stsci_pri_combo_mark_white.png) renders on GitHub but breaks on PyPI. Switch to an absolute raw.githubusercontent.com URL so the brandmark displays on both.

Closes #501.

[zacharyburnett]

I'm hesitant to say that removing the brandmark entirely is the best solution here

[karlhillx]

Fair enough. I can switch the image src to an absolute raw URL so the brandmark renders on PyPI too:
<img src="https://raw.githubusercontent.com/spacetelescope/stcal/main/docs/_static/stsci_pri_combo_mark_white.png" width="300"/>

Want me to pin to a commit SHA instead of main so old releases don't break retroactively? Either way, I can update the PR.

[zacharyburnett]

if we're going to point to a URL anyway then perhaps we should point to a central location

in general PyPI readme rendering is important so I'll bring it up with our upcoming templating work

[karlhillx]

Updated to keep the brandmark with an absolute raw.githubusercontent.com URL so it renders on PyPI too. If your templating work is going to centralize the logo URL anyway, happy to either land this as the interim fix or close in favor of that — your call.

[Copilot]

Pull request overview

This PR addresses PyPI README rendering by changing the README logo reference so it no longer depends on a relative path that breaks on PyPI.

Changes:

• Replaced the README logo <img> src from a relative path to an absolute raw.githubusercontent.com URL.

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