Fixed

• large images moving offscreen on open/scale
• pixel scaling sometimes missing a scroll event
• slight offcentering when zooming really far out

Added

• help menu, toggled with `?`. shows controls
• default folder icon when selecting a directory, as well as directory name
• enter into a directory when one is selected with enter
• back out to parent directory with backspace/alt+up
• broken image icon when the current image cannot be displayed, as well as filename
• flip image horizontally and vertically with f/shift+f
• retain image adjustments when scrolling between images with ctrl+left/right

Windows: `opti1.4.0.zip`
Linux:

• zipped folder: `opti1.4.0.tar.gz`
• standalone: `opti1.4.0.AppImage`