Polyfill: Fix type definition of Duration.toLocaleString

[printfn]

The options argument of Duration.toLocaleString is incorrectly typed as Intl.DateTimeFormatOptions which is incorrect. For example this code fails typechecking:

duration.toLocaleString('en', { style: 'digital' })`

TypeScript's lib.d.ts does not yet include type definitions for Intl.DurationFormat, so I've added the relevant options manually. This can be removed once TypeScript has shipped support.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.05%. Comparing base (9999373) to head (c393eb8).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3101   +/-   ##
=======================================
  Coverage   96.05%   96.05%           
=======================================
  Files          21       21           
  Lines        9951     9951           
  Branches     1802     1802           
=======================================
  Hits         9558     9558           
  Misses        346      346           
  Partials       47       47           

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[ptomato]

Thanks!