chore(scheduler-targets-alpha): readme updates

[gracelu0]

Issue # (if applicable)

Tracking: #31785

Reason for this change

Improve README quality.

Description of changes

Mostly grammar and formatting fixes.

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.17%. Comparing base (5d499dc) to head (134ad82).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #32123   +/-   ##
=======================================
  Coverage   77.17%   77.17%           
=======================================
  Files         105      105           
  Lines        7162     7162           
  Branches     1311     1311           
=======================================
  Hits         5527     5527           
  Misses       1455     1455           
  Partials      180      180           

Flag	Coverage Δ
suite.unit	77.17% <ø> (ø)

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Components	Coverage Δ
packages/aws-cdk	77.17% <ø> (ø)

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[aws-cdk-automation]

AWS CodeBuild CI Report

• CodeBuild project: AutoBuildv2Project1C6BFA3F-wQm2hXv2jqQv
• Commit ID: 134ad82
• Result: SUCCEEDED
• Build Logs (available for 30 days)

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[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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