FEATURE add includes Eel Helpers for String and Array

[Kleisli]

resolved:#2967
Added two new EelHelpers following the interface of the JavaScript functions String.prototype.includes() and Array.prototype.includes()

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/includes

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Checklist

• Code follows the PSR-2 coding style
• Tests have been created, run and adjusted as needed
• The PR is created against the lowest maintained branch
• Reviewer - PR Title is brief but complete and starts with FEATURE|TASK|BUGFIX
• Reviewer - The first section explains the change briefly for change-logs
• Reviewer - Breaking Changes are marked with !!! and have upgrade-instructions

[mhsdesign]

FYI just made this wip because it has to land in 8.4 but were working on branching it of

[mhsdesign]

Thanks for working on this!. I havent checked but the includes was just an example case.
Are there more helpful helpers that were missing?

Also i think we talked about that String.substr is deprecated in ecmascript and we should probably also add all deprecations like this here.

Or if you dont have the time for it we could of course only include those two helpers ... ^^

[mhsdesign]

we should probably use the 3 param (strict) to true or is the proposed way closer to ECMASCRIPT?

... also the (array) casts looks a little weird and im wondering in general if we should optimize and early return for the fromIndex=0 case?