v0.5.13-beta3

this release changes: (BETA)

• feature: tabs!
• feature: a global colorpicker
• feature: stroke width preset palette
• feature: added "semi-infinite" canvas layout ( thanks @D0V4HKIIN !)
• feature: added two-finger long-press touch gesture that switches the active pen (like stylus buttons)
• feature: added pdf import bitmap scaling preference
• UI: floating toolbars
• fix: lag when panning in "continuous-vertical" layout
• fix: layers when erasing marker strokes in "split-stroke" mode
• fix: "split-stroke" mode only eraser one segment at a time
• fix: freeze when saving multiple times in succession
• fix: blurry vector images after zooming in