Tiled 1.4.3

• Fixed running Tiled on macOS Big Sur (#2845)
• Fixed opening of files in already open instance of Tiled
• Fixed crash in Edit Commands dialog (#2914)
• Fixed Object Alignment not getting set when reloading a tileset
• Tile Collision Editor: Fixed invisible tile for isometric oriented tileset (#2892)
• Improved error message when adding external tileset
• Ignore attempts to replace a tileset with itself
• qmake: Support linking to system Zstd on all UNIX-like systems