update githook pre-commit because of egrep

-> egrep: warning: egrep is obsolescent; using grep -E

.githooks/pre-commit

@@ -6,8 +6,8 @@
 
 git diff --cached --name-status | egrep -i "^(A|M).*\.(md)$" | while read a b; do
   # YAML or TOML frontmatter?
-  (egrep "^---$" $b > /dev/null) && (cat $b | sed "/---.*/,/---.*/s/^lastmod:.*$/lastmod: $(date -u "+%Y-%m-%dT%H:%M:%S%z")/" > tmp)
-  (egrep "^\+\+\+$" $b > /dev/null) && (cat $b | sed "/+++.*/,/+++.*/s/^lastmod.*$/lastmod = '$(date -u "+%Y-%m-%dT%H:%M:%S%z")'/" > tmp)
+  (grep -E "^---$" $b > /dev/null) && (cat $b | sed "/---.*/,/---.*/s/^lastmod:.*$/lastmod: $(date -u "+%Y-%m-%dT%H:%M:%S%z")/" > tmp)
+  (grep -E "^\+\+\+$" $b > /dev/null) && (cat $b | sed "/+++.*/,/+++.*/s/^lastmod.*$/lastmod = '$(date -u "+%Y-%m-%dT%H:%M:%S%z")'/" > tmp)
   mv tmp $b
   git add $b
 done