gitrev kubkon/zig-yaml 8cf8dc3bb901fac8189f441392fc0989ad14cf71

Calculate line and col info indexed by token index. We can then
re-use this info to track current column number (aka indentation
level) of each "key:value" pair (map) or "- element" (list).
This significantly cleans up the code, and leads naturally to
handling of unindented lists in tbd files.