Add markdown linter

[martincostello]

• Add markdownlint.
• Update actionlint to the latest version.
• Update zizmor to the latest version.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.53%. Comparing base (6202ca9) to head (57e0613).
⚠️ Report is 1 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3673   +/-   ##
=======================================
  Coverage   94.53%   94.53%           
=======================================
  Files         111      111           
  Lines        3861     3861           
  Branches      778      778           
=======================================
  Hits         3650     3650           
  Misses        211      211           

Flag	Coverage Δ
Linux	94.53% <ø> (ø)
Windows	94.53% <ø> (ø)
macOS	94.53% <ø> (ø)

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[Copilot]

Pull request overview

This PR adds markdown linting to the project's CI workflow and updates existing linters to their latest versions. The changes include renaming the workflow file from actions-lint.yml to lint.yml and applying markdown formatting fixes throughout the documentation to comply with the new linter rules.

• Added markdownlint-cli2 for markdown file linting with configuration in .markdownlint.json
• Updated actionlint from v1.7.7 to v1.7.9 and zizmor from v1.14.1 to v1.16.3
• Applied markdown formatting fixes including proper heading syntax, table alignment, and blank lines

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.github/workflows/lint.yml	Renamed from actions-lint.yml, updated linter versions, and added markdownlint step
.github/zizmor.yml	Added configuration to disable new zizmor rules (concurrency-limits and dependabot-cooldown)
Swashbuckle.AspNetCore.slnx	Updated workflow file reference from actions-lint.yml to lint.yml
README.md	Added "Getting Started" heading and fixed table column alignment syntax
CONTRIBUTING.md	Fixed heading syntax from underlined style to ATX style (using # symbols)
docs/migrating-to-v10.md	Added blank line after code block for proper markdown formatting

Comments suppressed due to low confidence (1)

.github/workflows/lint.yml:9

• The paths-ignore configuration excludes **/*.md files, which means the workflow will not run when markdown files are modified in push events. This conflicts with the newly added markdown linting step (lines 53-58) that specifically checks markdown files.

Consider removing - '**/*.md' from the paths-ignore list so that markdown changes trigger the linter, or explicitly add paths for markdown files in the pull_request trigger to ensure markdown files are linted in PRs.

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