Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Prerequisites

• I'm using the latest version of Docusaurus.
• I have tried the npm run clear or yarn clear command.
• I have tried rm -rf node_modules yarn.lock package-lock.json and re-installing packages.
• I have tried creating a repro with https://new.docusaurus.io.
• I have read the console error message carefully (if applicable).

Description

Docusaurus checks for broken links inside tilde code blocks when onBrokenMarkdownLinks is set to throw

Reproducible demo

No response

Steps to reproduce

1. create a new docusaurus site using create-docusaurus
2. make sure that docusaurus.config.js contains

   onBrokenLinks: 'throw',
   onBrokenMarkdownLinks: 'throw',
   

3. Add following content to docs/intro.md

   ```
   this is an [invalid link](./path/to/a/page/that/does/not/exist.md)
   ```
   

4. run npx docusaurus build to see the site build as expected
5. change the codeblock from step 3 to use ~ instead of ` ie

   ~~~
   this is an [invalid link](./path/to/a/page/that/does/not/exist.md)
   ~~~
   

6. run npx docusaurus build to see the build fail with an error

   Error: Docs markdown link couldn't be resolved: (./path/to/a/page/that/does/not/exist.md) in 
   "/Users/foo/bar/baz/docusaurus/packages/testsite/docs/intro.md" for version current
       at Array.forEach (<anonymous>)
   

Expected behavior

Docusaurus either does not check links inside codeblock or checks them for both backtick and tilde codeblocks when onBrokenMarkdownLinks is set to throw

Actual behavior

Docusaurus errors for broken markdown links only inside tilde codeblocks when onBrokenMarkdownLinks is set to throw

Your environment

• Public source code: NA
• Public site URL: NA
• Docusaurus version used: Can reproduce with 2.0.0-beta.21 and 2.0.0-rc.1
• Environment name and version (e.g. Chrome 89, Node.js 16.4): Node.js 16.4
• Operating system and version (e.g. Ubuntu 20.04.2 LTS): Macos

Self-service

• I'd be willing to fix this bug myself.