feat(resources): add RxJS support into Slickgrid-Universal via external package

[ghiscoding]

This will add support of RxJS Observables with any Backend Services (like OData/GraphQL) which is the last missing piece for Angular-Slickgrid to finally use Slickgrid-Universal.

TODOs

• working POC of RxJS 6 support with Slickgrid-Universal
  • create new Example15 to demo RxJS
  • create new Example in Aurelia-Slickgrid to demo RxJS as well
• create an RxJS Facade (plain interface) to use within @slickgrid-universal/common package
• add RxJS code in all Services/Backend code
• add RxJS code in all Filters/Editors using collectionAsync
  • add collectionAsync with Observable into the demo to test Filter/Editor
• add unit tests
• add Cypress E2E tests (we can simply reuse Example 9 test suite)
• upgrade from RxJS 6 to 7
• rename/remove the Facade suffix from abstract class naming to avoid confusing for user of the lib (e.g. Angular-Slickgrid)
• final test in SF make sure is still working as expected

[codecov]

Codecov Report

Merging #280 (20d4f85) into master (ba703d8) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            master      #280    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files          209       212     +3     
  Lines        12523     12659   +136     
  Branches      4112      4146    +34     
==========================================
+ Hits         12523     12659   +136     

Impacted Files	Coverage Δ
packages/common/src/services/shared.service.ts	100.00% <ø> (ø)
...ackages/common/src/extensions/gridMenuExtension.ts	100.00% <100.00%> (ø)
packages/common/src/filters/autoCompleteFilter.ts	100.00% <100.00%> (ø)
packages/common/src/filters/filterFactory.ts	100.00% <100.00%> (ø)
packages/common/src/filters/filterUtilities.ts	100.00% <100.00%> (ø)
...ackages/common/src/filters/multipleSelectFilter.ts	100.00% <100.00%> (ø)
packages/common/src/filters/selectFilter.ts	100.00% <100.00%> (ø)
packages/common/src/filters/singleSelectFilter.ts	100.00% <100.00%> (ø)
packages/common/src/index.ts	100.00% <100.00%> (ø)
...ages/common/src/services/backendUtility.service.ts	100.00% <100.00%> (ø)
... and 18 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ba703d8...20d4f85. Read the comment docs.