Changes in diff order:
- remove github as the second HOMEPAGE (it's already in remote-id)
- simplify & automatize ZIG_SLOT assignment
- also moved comment there so it's clearer
- simplify SRC_URI assignment
- use ZIG_SLOT in SLOT
- introduce minimum_runtime_zig_version
- unquote DOCS contents
- remove obsolete pkg_postinst
Signed-off-by: Filip Kobierski <fkobi@pm.me>