Add doctoc's check for changelog files

[zhzhuang-zju]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:

The TOC for the Changelogs file is automatically generated using doctoc. To facilitate the review of the Changelogs file, the doctoc's check has been added.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[karmada-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign rainbowmango for approval. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• .github/workflows/OWNERS
• docs/CHANGELOG/OWNERS
• hack/OWNERS

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[zhzhuang-zju]

https://github.com/karmada-io/karmada/actions/runs/12348206301/job/34456600216?pr=5956#step:6:36
no cached repository for helm-manager-54d2620bbb6f1bb3f35d4c7f945bfa25077949488dcbb0a4d01c90f2c35baa59 found. (try 'helm repo update')

/retest

[RainbowMango]

/retest

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.18%. Comparing base (5fbcf9b) to head (4c9b501).

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5956      +/-   ##
==========================================
- Coverage   48.18%   48.18%   -0.01%     
==========================================
  Files         664      664              
  Lines       54799    54799              
==========================================
- Hits        26405    26403       -2     
- Misses      26680    26682       +2     
  Partials     1714     1714              

Flag	Coverage Δ
unittests	48.18% <ø> (-0.01%)	⬇️

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