refactor: office xml addin string and readme

[ZYUN-MSFT]

This PR did the following:

1. modify create step by step office xml addin entry icon
2. modify create step by step office xml addin string
3. modify office xml addin readmes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.12%. Comparing base (c30ec89) to head (f449fc5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #11082   +/-   ##
=======================================
  Coverage   87.12%   87.12%           
=======================================
  Files         456      456           
  Lines       27468    27468           
  Branches     5516     5516           
=======================================
  Hits        23931    23931           
  Misses       1777     1777           
  Partials     1760     1760           

Files	Coverage Δ
packages/fx-core/src/question/create.ts	91.54% <100.00%> (ø)
...-core/src/question/options/CreateProjectOptions.ts	100.00% <ø> (ø)