WIP on update to zig 0.16

[Cohors1316]

Work is in progress to bring the project up to date with zig master. Currently all dependencies and jetzig lib are passing zig-0.15.2, work is ongoing on the cli.

[Cohors1316]

zig-0.15 branch is passing everything I can think to throw at it. All current built in tests are passing.

There are some breaking changes, notably markdown fragments have been replaced with formatter functions from zmd.

zmpl now uses incremental compilation for templates, with each one compiling into individual .zig files that are then imported into the manifest.

If you find any issues please pop into the discord if you can as there's more eyes there. If you hate discord I've also popped up #jetzig on libera.

Fastest way to get up and running is with the flake, nix shell github:jetzig-framework/jetzig/zig-0.15