With the addition of `--banner` option index files no longer start with '// @create-index'
This new regex looks for '// @create-index' that are either at the beginning of the file (old behavior) or if it is followed by a newline.
Basically it just checks whether it exists in a file or not.
Added a test for it now.
# Conflicts:
# src/utilities/validateTargetDirectory.js
`--resursive`: Create/update index files recursively. Halts on any unsafe "index.js" files.
`--ignore-unsafe`: Ignores unsafe "index.js" files instead of halting.
