document a couple of miscellaneous helpers

Dependencies

• [2] N2NUGNN4 include a brief reference enabling many useful apps

Change contents

• edit in reference.md at line 319
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  +

  + * `array.find(arr, elem)` -- scan table `arr` for `elem` assuming it's

  + organized as an array (just numeric indices).
• edit in reference.md at line 323
  [2.12436]

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  + * `array.any(arr, f)` -- scan table `arr` for any elements satisfying

  + predicate `f`. Return first such element or `false` if none.

  +