Really like what you are going for here. I've actually been working on a similar system of a minimalist static site generator off and on for about a year. Looking forward to having a more in depth look at your approach.. and congrats for putting it out there, I've been letting my imposter syndrome keep me from publicly showing my system off. I really dig your templating system, I ended up going with Handlebars but I always planned on removing it at some point. Are you using grey matter for parsing the markdown metadata or did you create your own parser?
Hey thanks! Can definitely empathize with the imposter syndrome, it's a tough hurdle to clear.
For the templating system I decided to also add an option to define your own if you don't like the [] syntax (https://prpl.dev/api#options). Figured since the system is regex-based instead of AST-based there's no reason not to expose it as an option to users.
For the metadata I implemented a basic parser. Here's a link to that part of the source code, it's not the most efficient nor does it cover all the edge cases, but it's simple enough it can be easily updated (https://github.com/tyhopp/prpl/blob/master/packages/core/src...).
Good luck and hope I can see your system on HN someday too