Update SPM readme and CI Xcode version

[cacheung]

Update SPM readme and CI Xcode version

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codecov]

Codecov Report

Merging #60 (c50764c) into main (11f53ab) will increase coverage by 3.70%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #60      +/-   ##
==========================================
+ Coverage   88.80%   92.50%   +3.70%     
==========================================
  Files          28       28              
  Lines        2188     2188              
==========================================
+ Hits         1943     2024      +81     
+ Misses        245      164      -81