hxltmcli: HXLTM additional file for advanced processing (YAML-like, as opposed to table-like)

[fititnt]

Related:
-hxltmcli .asa.hxltm.json / .asa.hxltm.yml: HXLTM Abstractum Syntaxim Arborem #3
-hxltmcli (or equivalent cli): MVP of custom ouput based on template + HXLTM data as cli option (without need of Ruby) #4

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This topic is about at least an Minimal Viable Product of additional instruction to process what HXLTM files would means. While the reference implementation would be the hxltmcli tool, one idea is this file try to be as independent as possible.

For example, if necessary, instead of embed python code, keep the trend of use templating system like Liquid (https://shopify.github.io/liquid/). Liquid also somewhat provide some level of minimal ad hoc virtual machine (since good implementation would only expose and allow export special context; but we don't make official opinion on this at the moment, since would requrie audit the current python livrary that process liquid template); but note that even such ad hoc VM cannot process DDoS, so if someone make infinite loop by accident we could not prevent it.