Disable markdownlint rule MD026

Although I think it is generally a sensible rule, I decided that this is just too uptight. It will be better to focus our
efforts on compliance with the rules for more significant issues.

Author: per1234

.markdownlint.yml

@@ -31,8 +31,7 @@ MD024: false
 MD025:
   level: 1
   front_matter_title: '^\s*"?title"?\s*[:=]'
-MD026:
-  punctuation: ":"
+MD026: false
 MD027: false # Prettier
 MD028: false
 MD029: