[Feature request] Allow customization of the "Edit on GitHub" links

[simurai]

Currently it doesn't seem possible to configure the "Edit on GitHub" links in the footer. I think it would be needed to fix this issue https://github.com/primer/view_components/issues/1310 in PVC.

• Maybe an option to just hide the "Edit on GitHub" links, see comment.
• Or a way to configure the ${defaultBranch}/${filePath} part. But in PVC's case it's complicated because some of the docs are under /docs/content. But the components are documented in the same file as the source code. E.g. /app/components/...