Add user parking feature with configurable settings

[sokripon]

Add option to park idle users at screen edges instead of removing them

New Options

• --park-idle-users - Enable parking (move idle users to screen edge instead of removing)
• --park-immediate - Park users as soon as they go idle
• --park-lock-slots - Keep parking slots reserved once claimed
• --park-position POSITION - Where to park: bottom, top, left, or right
• --park-direction-reverse - Reverse the fill direction
• --park-y-offset PIXELS - Distance from the screen edge (default: 0)
• --park-spacing PIXELS - Spacing between parked users (0 = auto)
• --park-opacity FLOAT - Opacity of parked users (default: 0.5)
• --park-scale SCALE - Scale of parked users (default: 0.5)
• --park-speed-factor F - Speed multiplier while parking (default: 0.5)
• --park-rows ROWS - Number of rows for parked users (0 = auto, default: 1)
• --park-round-robin - Distribute users across rows in round-robin order

Example:

./gource -s 0.1 --park-scale 0.5 --park-opacity 0.5 --park-rows 2  --park-position bottom --park-immediate --park-lock-slots  --park-round-robin ./

2025-12-30.14-08-58.mp4

Example with user images, as the main point of this is to keep showing contributers

./gource -s 0.1 --park-idle-users --park-scale 0.5 --park-opacity 0.5 --park-rows 2  --park-position bottom --park-lock-slots  --park-round-robin --park-immediate --user-image-dir ./avatars2/ ./

2025-12-30.14-19-21.mp4