feat: add Custom Global Item Data Provider

[ghiscoding]

• allow providing a custom global item metadata provider by passing it through the groupItemMetadataProvider DataView constructor option
• implementation copied from https://github.com/GerHobbelt/SlickGrid fork

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.0%. Comparing base (a04fb21) to head (fe0f905).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1794   +/-   ##
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  Coverage   100.0%   100.0%           
=======================================
  Files         187      187           
  Lines       34065    34069    +4     
  Branches    10133    10135    +2     
=======================================
+ Hits        34039    34043    +4     
  Misses         26       26           

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