Rule Request: Check that files only contain only valid characters

[rupreck]

Under the YAML spec there are only certain characters supported however often editors add hidden characters such as non breaking spaces. Finding these would be helpful.

See: https://yaml.org/spec/1.2.2/#51-character-set

A simple regex, such as this one might be used that finds characters that are not printable unicode characters:

[^\x09\x0A\x0D\x20-\x7E\x85\xA0-\uD7FF\uE000-\uFDCF\uFDF0-\uFFFD]