Option to allow eslint-disable comment before the header

[Leomaradan]

By default, in VSCode, the option for disabling a eslint rule for the whole file place the comment on top of the file, before the header. That cause the header rule to be invalid, and the eslint comment must be moved manually

This PR add an option allowDisableFirst. When enabled, the eslint-disable comment are ignored from the getLeadingComments function

[Stuk]

Thanks for the PR! Would you mind adding a test?

[bonkalol]

Must have option here