README: broken links

[alexandrascript]

Hey folks,

The "here" link about opaque URL on line 83 of the README isn't working.

Therefore the URL of the ad is an opaque url (details here) — which can be used for rendering, but cannot be inspected directly.

I believe it should be updated to: https://github.com/shivanigithub/fenced-frame/blob/master/explainer/opaque_src.md

And I recommend updating the sentence for clarity, as there are often 2 URLs associated with an ad (the URL for the creative that loads in the ad slot and the URL that a user can click on, the conversion URL).

Therefore, the URL for the ad creative is an opaque url — which can be used for rendering, but cannot be inspected directly.

[alexandrascript]

Looks like several files were moved into sub-directories. Another example:

Unpartitioned storage access

The challenges of this use case is detailed in the document here.

Should be updated to:

Unpartitioned storage access

The challenges of this use case is detailed in Fenced frames and promptless unpartitioned storage access.

[shivanigithub]

Thanks for the issue!
Updated both the links and the text for clarity.