feat: the UI part for the API Plugin template

[huimiu]

https://msazure.visualstudio.com/Microsoft%20Teams%20Extensibility/_workitems/edit/27000310

• Replace the target template for the copilot plugin from scratch scenario.
• Update the README.md.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.16%. Comparing base (70bf02f) to head (8583405).
Report is 1 commits behind head on dev.

Additional details and impacted files

@@           Coverage Diff           @@
##              dev   #11104   +/-   ##
=======================================
  Coverage   87.16%   87.16%           
=======================================
  Files         457      457           
  Lines       27620    27621    +1     
  Branches     5560     5560           
=======================================
+ Hits        24074    24075    +1     
  Misses       1778     1778           
  Partials     1768     1768           

Files	Coverage Δ
...ackages/fx-core/src/component/coordinator/index.ts	88.48% <100.00%> (+0.02%)	⬆️

... and 1 file with indirect coverage changes