Make grep exit with 0

grep exits with 1 if there is no match found,
which makes the pipeline fail due to the pipefail
option
Also make grep case insensitive

build/build.sh

@@ -85,7 +85,10 @@ fi
 # Spellcheck
 if [ "${SPELLCHECK:-}" = "true" ]; then
   export ASPELL_CONF="add-extra-dicts $(pwd)/build/assets/custom-dictionary.txt; ignore-case true"
-  pandoc --lua-filter spellcheck.lua output/manuscript.md | uniq | while read word; do grep -on "\<$word\>" content/*md; done | sort -h -t ":" -k 1b,1 -k2,2 > output/spelling-errors.txt
+  # Use "|| true" after grep because otherwise this step of the pipeline will
+  # return exit code 1 if any of the markdown files do not contain a
+  # misspelled word
+  pandoc --lua-filter spellcheck.lua output/manuscript.md | uniq | while read word; do grep -ion "\<$word\>" content/*.md; done || true | sort -h -t ":" -k 1b,1 -k2,2 > output/spelling-errors.txt
   cat output/spelling-errors.txt
 fi