Migration 5.0

Breaking changes and highlights of the 5.0 major.
  1. Removal of @koalarx/utils/light
  2. Opt-in holidays: date-holidays becomes an optional peer (install in your project + import '@koalarx/utils/holidays')
  3. KlArray.map / KlString.split return KlArray
  4. New operators and prototypes subpaths
  5. Internal core/ layout (stable public imports)
  6. Web docs + llms.txt generated from Markdown sources