It looks like GitHub doesn't follow symlinks, so in GitHub's preview does not correctly follow any links to files in the symlinked directory documentation/docs/assets/hardware. I will wait to see whether Zettlr (which is used by @tcebron) correctly follows symlinks; if not (or if we decide that broken hardware asset links in the GitHub preview are intolerable), we might have to move all hardware design files from hardware into documentation/docs/assets/hardware and change hardware to be a symlink to documentation/docs/assets/hardware.

I think this is an improvement over the current DX, and I don't think there are any regressions with it, so I'm going to merge this PR now even though @tcebron hasn't tested how well it works with Zettlr yet. If we later decide we want to move everything in /hardware into /documentation/docs/assets/hardware and replace the former with a symlink to the latter (i.e. reversing the current symlink directionality), we can do that in a future PR.