fix: update devcontainer postCreateCommand

[KentHsu]

Description

Refer to dotnet-dsk to add a postCreateCommand script and update devcontainer.json to run this script in postCreateCommand When working with dev container, all tests show up in VSCode testing tab and pass successfully

Issue reference

Please reference the issue this PR will close: #702

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• [X] Code compiles correctly
• [X] Created/updated tests
• [X] Extended the documentation