Add 'experimental' tags to package.json for pylance experiment

[rchiodo]

For #https://github.com/microsoft/vscode-jupyter-internal/issues/246

[rchiodo]

Still need to force enable this in the preview version of the extension.

[IanMatthewHuff]

Something odd going on with the checks on this?

Edit: NVMD, same thing happening with my PR. Looking now.

[codecov-commenter]

Codecov Report

Merging #8687 (7861425) into main (c60dcfd) will increase coverage by 0%.
The diff coverage is 85%.

❗ Current head 7861425 differs from pull request most recent head 5bf608f. Consider uploading reports for the commit 5bf608f to get more accurate results

@@          Coverage Diff          @@
##            main   #8687   +/-   ##
=====================================
  Coverage     71%     71%           
=====================================
  Files        384     384           
  Lines      24666   24670    +4     
  Branches    3794    3796    +2     
=====================================
+ Hits       17655   17662    +7     
+ Misses      5469    5466    -3     
  Partials    1542    1542           

Impacted Files	Coverage Δ
src/client/extensionActivation.ts	94% <50%> (-2%)	⬇️
src/client/common/types.ts	100% <100%> (ø)
...ence/notebook/intellisense/intellisenseProvider.ts	80% <100%> (+<1%)	⬆️
...ience/variablesView/variableViewMessageListener.ts	77% <0%> (-23%)	⬇️
...ent/common/application/webviewViews/webviewView.ts	67% <0%> (-11%)	⬇️
...atascience/interactive-window/interactiveWindow.ts	67% <0%> (-1%)	⬇️
src/client/debugger/jupyter/kernelDebugAdapter.ts	77% <0%> (+<1%)	⬆️
src/client/datascience/raw-kernel/rawSocket.ts	84% <0%> (+1%)	⬆️
src/client/datascience/dataScienceSurveyBanner.ts	75% <0%> (+6%)	⬆️