fix: support fallback for media src

[srijitcoder]

Implemented Changes

Problem

When uploading media using the GitHub API in git-clerk, we can only use its permanent URL. This ensures the media is always accessible, even if the branch is merged or deleted. However, the permanent URL becomes available to users only after a delay of one minute.

Solution

• Utilize the commit URL as a fallback src. While the commit URL is not suitable for permanent purposes, it is available immediately after merging. This allows the image to be loaded into storytelling until the permanent URL is ready. (This ensures users can view the image without delay.)
• To achieve this, we use the attribute data-fallback-src="" property to load the backup URL, as shown below:

<img src="permanent-src" data-fallback-src="temporary-fallback-src"

• If any normal image don't load a default fallback-src will be loaded - https://placehold.co/600x400?text=Media+not+found

Screenshots/Videos

Checklist before requesting a review

• I have performed a self-review of my code
• I have added a test related to this feature/fix
• For new features: I have created a story showcasing this new feature
• All checks have passed
• The PR title follows conventional commit style and reflects the type of change (major/minor/patch, breaking)
• The PR title describes the change within this element (each merged PR equals one entry in the element's changelog!)

[netlify]

✅ Deploy Preview for eoxelements ready!

Name	Link
🔨 Latest commit	d1bc14c
🔍 Latest deploy log	https://app.netlify.com/sites/eoxelements/deploys/6790c64c22f2b70008edd486
😎 Deploy Preview	https://deploy-preview-1490--eoxelements.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.