Shotcut 21.10.31

What's new in this version:

Fixed:
- export to MP4 or MOV may not give constant frame rate (broke in v21.09.20)
- Properties > Speed with GoPro .LRV proxy file (broke in v21.09.20)
- Export > Reset did not deselect a preset

- Changed Ctrl+Shift+V in Text: Simple to paste
- Changed the color of an alert vs. the proxy/preview-scaling status messages
- Increased the time for some messages, and added the ability to click a message to dismiss it
- Upgraded FFmpeg to version 4.4.1

Added:
- help message boxes to the Mask: Simple Shape, Mask: From File, and Text: Rich filters
- Properties > Comments for color clips
- a Mask: Chroma Key filter for convenience, for example secondary color correction
- support for multiple selected clips to the timeline Cut, Copy, Paste, Overwrite, and Append operations

- Copy exclusively uses the system clipboard in this mode and does not show in the Source player
- Added Markers to the Timeline
- Click toolbar button or press M the first time to add a marker at the playhead (current position) with no dialog
- Markers appear in the time ruler/track/row at the top of the Timeline
- A marker shows a tool tip with its name and time when you hover the mouse over it
- Click a marker to seek to it
- Click toolbar button or press M when the playhead is on the exact start time of a marker to open the Edit dialog where you can change the name, color, start, and end times
- A color change is remembered for all new markers until changed
- Right-click a marker to open its context menu to Edit or Delete a marker
- Press Ctrl+Shift+M when the playhead is on the exact start start time of a marker to Delete it
- Drag a marker to move it
- Ctrl+drag (command on macOS) a marker to changes its duration (a marker with a duration longer than one frame is also called a Range)
- Export > From lists all Ranges
- Markers are saved to the project file and reloaded with the project XML in a <properties name="shotcut:markers"> element
- Marker operations support Undo and Redo