.ignore v3.0.0

Implemented enhancements:

• Separated builds for different IDE versions (139-181+)
• Abandoned support for <139
• Integration with IntelliJ Plugin Verifier

Fixed bugs:

• Argument for @NotNull parameter 'settings' of HideIgnoredFilesTreeStructureProvider.modify must not be null #551
• Projects leak in ExternalIndexableSetContributor.CACHE #553
• Unable to save settings #552