v0.5.0

• find a texture from a similar image. useful for screenshots
• a failed export no longer leaves a truncated file behind
• set LLTEXTURECACHE_LOG env var to see debugging information
• the app hands its exit code back
• bumps texture-courier dependency, bringing in some minor improvements
• right click menu on the inspector, with the alpha mode shown in it
• drag and drop in the inspector
• better tooltip for the inspector preview
• rename "Transparency Mode" to "Alpha Mode", and "Grid" to "Checkerboard"
• fix sticky swatches
• render alerts as a dialog instead of a line in the status bar