fix(contented-pipeline-md): replace \n in description to fix SEO

[fuxingloh]

What this PR does / why we need it:

As per title.

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[codecov]

Codecov Report

Merging #579 (57c8a8a) into main (0551e1b) will decrease coverage by 6.93%.
Report is 23 commits behind head on main.
The diff coverage is 41.33%.

@@            Coverage Diff             @@
##             main     #579      +/-   ##
==========================================
- Coverage   85.00%   78.07%   -6.93%     
==========================================
  Files          10       12       +2     
  Lines         420      488      +68     
  Branches       73       88      +15     
==========================================
+ Hits          357      381      +24     
- Misses         63      107      +44     

Files Changed	Coverage Δ
...contented-pipeline-md/src/plugins/RehypeHeading.ts	87.09% <ø> (ø)
...contented-pipeline-md/src/plugins/RehypeMermaid.ts	43.75% <ø> (ø)
...es/contented-pipeline-md/src/plugins/RemarkLink.ts	71.42% <ø> (ø)
packages/contented-pipeline/src/Pipeline.ts	85.33% <ø> (ø)
...ages/contented-processor/src/ContentedProcessor.ts	86.41% <ø> (ø)
...ntented-pipeline-md/src/plugins/RemarkCodeblock.ts	16.12% <16.12%> (ø)
...s/contented-pipeline-md/src/plugins/RehypeShiki.ts	41.93% <41.93%> (ø)
...ages/contented-pipeline-md/src/MarkdownPipeline.ts	85.29% <100.00%> (ø)
...ages/contented-pipeline-md/src/UnifiedProcessor.ts	87.09% <100.00%> (-0.41%)	⬇️
...ented-pipeline-md/src/plugins/RemarkFrontmatter.ts	76.78% <100.00%> (+3.31%)	⬆️