v0.2.0

this release changes:

• an updated icon!
• an updated file format. !!! Breaks compatibility to older versions. Please export existing files before upgrading / downgrade temporarily (explained how to downgrade at github.com/flxzt/rnote)
• new features: PDF import, clipboard and drag&drop support
• performance improvements in stroke rendering, selecting, erasing by parallelizing these operations
• UI improvements
• internal: code refactoring into ECS pattern
• bug fixes