Improve USFM and TN link checking, etc.

[RobH123]

This change is 

[codecov]

Codecov Report

Merging #55 into master will decrease coverage by 4.19%.
The diff coverage is 30.48%.

@@            Coverage Diff             @@
##           master      #55      +/-   ##
==========================================
- Coverage   52.06%   47.87%   -4.20%     
==========================================
  Files          20       20              
  Lines        1961     2047      +86     
  Branches      614      643      +29     
==========================================
- Hits         1021      980      -41     
- Misses        569      666      +97     
- Partials      371      401      +30     

Impacted Files	Coverage Δ
src/core/getApi.js	10.12% <0.00%> (-0.40%)	⬇️
src/core/markdown-text-check.js	81.81% <ø> (ø)
src/core/text-handling-functions.js	91.30% <0.00%> (+13.04%)	⬆️
src/core/manifest-text-check.js	10.20% <19.04%> (-49.38%)	⬇️
src/core/tn-links-check.js	69.34% <21.95%> (-17.45%)	⬇️
src/core/usfm-text-check.js	58.10% <33.33%> (+0.06%)	⬆️
src/core/tn-table-row-check.js	70.61% <47.05%> (-4.98%)	⬇️
src/core/ta-reference-check.js	95.55% <50.00%> (ø)
src/core/tn-table-text-check.js	64.60% <56.00%> (-5.51%)	⬇️
src/core/field-text-check.js	54.70% <66.66%> (-0.96%)	⬇️
... and 5 more

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[PhotoNomad0]

Reviewed 3 of 10 files at r1, 31 of 31 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved

[PhotoNomad0]

Reviewed 1 of 1 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved