feat(frontend): prerender canonical URL for subpages

[peterpeterparker]

Motivation

I'm not entirely sure this is a strict requirement for a SPA, even if the pages are prerendered, since each page is behind a login screen and ultimately rendered with JavaScript. However, while reviewing a PR in Internet Identity, it crossed my mind that it might be more accurate to use a canonical URL - and correspondingly an og:url - that reflects each subpage’s actual path rather than always pointing to the root. So, this PR introduces a similar change to what I just implemented for Juno (PR) and OISY (PR).

Test

I tested the change locally, but it definitely needs to be verified the next time you deploy to any environment.

Notes

I'm really not certain this is necessary, so feel free to reject and close the PR if you don’t think it adds value.

Changes

• Added a script to update the canonical and og:url after build
• Chained the script in the post-process step before calculating the CSP