feat(css): Add white-space-pre-line utility

What does this MR do?

This adds a gl-white-space-pre-line CSS utility, this prevents pre HTML elements from adding the left marging, e.g.

Default pre CSS	with white-space: pre-line

Does this MR meet the acceptance criteria?

Conformity

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• Added the ~"component:*" label(s) if applicable.

Security

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• Label as security and @ mention @gitlab-com/gl-security/appsec
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