chore: bump markdownlint-cli2 from 0.18.1 to 0.20.0

[delei]

Purpose of the pull request

Related: #862

What's changed?

• bump markdownlint-cli2 from 0.18.1 to 0.20.0 in package.json
• update markdownlint-cli2 config file
• fix the issues detected by markdownlint scanning

Test

> markdownlint-cli2 --config ./.markdownlint-cli2.jsonc "./**/*.md" "#node_modules"

markdownlint-cli2 v0.20.0 (markdownlint v0.40.0)
Finding: ./**/*.md !node_modules website/**/*.md !**/node_modules/** !**/target/** !**/dist/**
Linting: 101 file(s)
Summary: 0 error(s)

Checklist

• I have read the Contributor Guide.
• I have written the necessary doc or comment.
• I have added the necessary unit tests and all cases have passed.

[psxjoy]

LGTM