Add Bash syntax highlighting to README.md

[Benjamin-Loison]

Description

Suggested changelog entry

Related issues/external references

Fixes #

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
  • This change is only breaking for integrators, not for external standards or end-users.
• Documentation improvement

PR checklist

• I have checked there is no other PR open for the same change.
• I have read the Contribution Guidelines.
• I grant the project the right to include and distribute the code under the BSD-3-Clause license (and I have the right to grant these rights).
• I have added tests to cover my changes.
• I have verified that the code complies with the projects coding standards.
• [Required for new sniffs] I have added XML documentation for the sniff.
• [Required for new files] I have added any new files to the package.xml file.

[jrfnl]

You may want to have a read through #3932...

[Benjamin-Loison]

You may want to have a read through #3932...

I paid attention to PRs but not issues, my bad, thank you I will pay attention to issues next time.

I close this PR in favor of PHPCSStandards/PHP_CodeSniffer#121.