fix: leave whitespace only lines alone

[UziTech]

Marked version: v1.2.7

Description

The whitespace is removed from lines with only whitespace. This causes problems in code blocks where the whitespace matters.

This PR keeps the spaces in blank lines and adds them to output.

This PR also adds a new line character to the end of all code blocks.

• Fixes Lines with only spaces are removed, even in code blocks #1884

Contributor

• Test(s) exist to ensure functionality and minimize regression

Committer

In most cases, this should be a different person than the contributor.

• CI is green (no forced merge required).
• Squash and Merge PR following conventional commit guidelines.

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[UziTech]

@davisjam Could you check these regexps for redos vulnerability?

/^(?: *(?:\n|$))+/
/^( {4}[^\n]+(?:\n(?: *(?:\n|$))*)?)+/

[UziTech]

I tried testing those regexes with everything that I could think might cause redos and nothing would cause it so I think they are good.

[github-actions]

🎉 This PR is included in version 1.2.8 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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