Signature Embedding on Android and iOS

What's Changed

• view saved pdf and open by @Lilytreasure in #3
• saved docs load fix by @Lilytreasure in #4
• added signature functionality by @Lilytreasure in #5
• signature embedding on android by @Lilytreasure in #6
• iOS signature embedding by @Lilytreasure in #7

Full Changelog: 1.02...1.03