Add HumanizeVisitor and Calculator#humanize

[MaximilianoGarciaRoe]

Why

Apps that expose Dentaku formulas to end users (HR tools, business-rule
engines, approval workflows) have no way to explain what a formula means
in plain language. This fills that gap.

calc = Dentaku::Calculator.new

calc.humanize('IF(tenure >= 2, base * 1.1, base)')
# => "if tenure is greater than or equal to 2 then base times 1.1 else base"

calc.humanize('days >= min and days <= max', min: 5, max: 20)
# => "days is greater than or equal to 5 and days is less than or equal to 20"

What

HumanizeVisitor < PrintVisitor — overrides only the output, inherits
everything else. Falls back to PrintVisitor for any unmapped node, so
custom functions still render.

Covers all built-in constructs: arithmetic, comparison, logical and
bitwise operators, IF / SWITCH / CASE, all numeric, string, and
collection functions, and the full Ruby Math module.

Lazy-loaded — no overhead unless #humanize is called.

Notes

• Phrase wording ("times" vs "multiplied by", etc.) is easy to adjust.
• i18n is out of scope but the phrase table is one hash — straightforward
  to externalize later if wanted.
• Happy to drop Calculator#humanize if you prefer the visitor standalone.

Happy to contribute and looking forward to any feedback or suggestions!

[DirkDoes]

be carefull what features you use of Ruby, since Dentaku even supports 2.5 which does not contain all the quality of life features.
For instance you are using args[1..] which is not supported in ruby 2.5 (or specifically the 1.. endless range)
Instead you should use args[1..-1] to not make it an endless range, or just args.drop(1)

Just realized that 2.5 will not be supported later. so i think its just matter up re-syncing it with main