Fix bug with repoCode for linked articles; add test for newLine in TN single line field that crashed tC build

[RobH123]

This change is 

[codecov]

Codecov Report

Merging #206 (1a81779) into master (9f22465) will decrease coverage by 0.02%.
The diff coverage is 31.76%.

@@            Coverage Diff             @@
##           master     #206      +/-   ##
==========================================
- Coverage   30.05%   30.02%   -0.03%     
==========================================
  Files          29       29              
  Lines        4279     4339      +60     
  Branches     1583     1616      +33     
==========================================
+ Hits         1286     1303      +17     
- Misses       1817     1835      +18     
- Partials     1176     1201      +25     

Impacted Files	Coverage Δ
src/core/questions-tsv7-row-check.js	2.77% <0.00%> (-0.19%)	⬇️
src/core/twl-tsv6-row-check.js	2.90% <0.00%> (-0.22%)	⬇️
src/core/notes-links-check.js	20.76% <13.04%> (-0.10%)	⬇️
src/core/notes-tsv7-row-check.js	62.70% <53.33%> (-1.04%)	⬇️
src/core/tn-tsv9-row-check.js	59.55% <62.50%> (-0.33%)	⬇️
src/core/markdown-file-contents-check.js	38.88% <66.66%> (+0.31%)	⬆️
src/core/markdown-text-check.js	56.29% <100.00%> (+0.65%)	⬆️

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[RobH123]

A small one this time with one bug fix and one new check.

[mandolyte]

Reviewed 1 of 5 files at r1, 14 of 14 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @RobH123)