Properly resolve all links to source code on the `dev` version of the docs

[critesjosh]

On the dev version of the docs, the fallback tag is master, but the latest docs are actually being built on the next branch. aztec.js and aztec.nr versions are also referencing master. this will resolve properly for aztec.nr, since noir fetches code from github, but since there are no npm packages published based on the master code, these will not work. simply updating the master tag to next will fail for similar reasons.

Options:

• update the latest tag to be the latest nightly release. there is still an edge case where the source code on next differs from the last nightly release, if an engineer merges changes to that code that day
• cut a new nightly version tag as part of the nightly release every night. delete the old nightly version in the docs. this is a bit more work to set up but should work correctly for all cases when done