Expose a Validation & Summary CLI tool

[EZoni]

We automatically have a validation mode in the Python implementation from pydantic. That is also useful to provide guidance to developers and users who write their own lattice files in a chosen format (e.g., YAML), through automatic validation, error messages (what a parameter should be, where it should be, etc.), and a short summary of what we found after parsing the file.

[ax3l]

Since the validation and error message come "for free" with our Python implementation, what this issue means is: we will implement a CLI tool/hook that reads a PALS file (of any of our supported formats) and "does nothing" to it besides report back:

• errors while parsing
• a few characteristics of the lattice that was parsed (e.g., N elements and total lattice lengths of ... meters).

Example tools that do something like this:

• openPMD-validator
• openPMD-ls

All we need for this is to provide an entry_point in our Python installer to expose a "CLI tool" that calls a function to read and print statistics. An entry point adds CLI functionality to Python projects, which can then be installed easily, e.g., with pipx.