Account for separating spaces when parsing the disabled rules.

[PaulWoitaschek]

IntelliJ reformats the disabled_rules of the editor config and adds spaces between the entries.

For example:

[*]
disabled_rules = import-ordering,filename,trailing-comma

Will be reformatted to:

[*]
disabled_rules = import-ordering, filename, trailing-comma

With the whitespace included, ktlint does not pick up these rules.

This PR accounts for these white spaces and modifies the existing tests to also cover this scenario.

[shashachu]

thanks for the contribution!