feat(core): expose all Extensions in new getter prop & fix draggable

[ghiscoding]

• also renamed the SharedService.grid to SharedService.slickGrid to align with the vanilla bundle slickGrid property
• also fixed the Draggable Grouping example that was not working, apparently the option enableColumnReorder can be a callback function as well as a boolean

[codecov]

Codecov Report

Merging #29 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #29      +/-   ##
==========================================
+ Coverage   99.60%   99.60%   +0.01%     
==========================================
  Files         185      185              
  Lines       10008    10017       +9     
  Branches     3401     3402       +1     
==========================================
+ Hits         9967     9976       +9     
  Misses         41       41              

Impacted Files	Coverage Δ
...ages/common/src/enums/gridAutosizeColsMode.enum.ts	100.00% <ø> (ø)
packages/common/src/enums/gridStateType.enum.ts	100.00% <ø> (ø)
packages/common/src/enums/index.ts	100.00% <100.00%> (ø)
...ages/common/src/extensions/autoTooltipExtension.ts	100.00% <100.00%> (ø)
...src/extensions/cellExternalCopyManagerExtension.ts	100.00% <100.00%> (ø)
...ackages/common/src/extensions/cellMenuExtension.ts	100.00% <100.00%> (ø)
...common/src/extensions/checkboxSelectorExtension.ts	100.00% <100.00%> (ø)
...ges/common/src/extensions/columnPickerExtension.ts	100.00% <100.00%> (ø)
...ages/common/src/extensions/contextMenuExtension.ts	100.00% <100.00%> (ø)
...ommon/src/extensions/draggableGroupingExtension.ts	100.00% <100.00%> (ø)
... and 10 more

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