SerialTerm Release 0.2.0

Full key pass through, so vi, nano and htop now work over the connection.

Breaking: ESC no longer exits. Every key is sent to the connected device, and SerialTerm's own commands sit behind an escape key, Ctrl+A by default — Ctrl+A ? for help, Ctrl+A q to quit, Ctrl+A Ctrl+A to send a literal Ctrl+A. Use --escape-key to move it, or --legacy-keys to bring the old F1-F5, Home and ESC bindings back.

• Arrows, Home/End, Delete and the function keys send the escape sequence a real terminal sends, instead of a null byte
• ANSI output is now interpreted (ENABLE_VIRTUAL_TERMINAL_PROCESSING), so full screen programs draw properly — this is why vi had no status footer
• Device output passes through as raw bytes. It was being decoded as ASCII, which replaced every byte above 127 with ?
• A port held open by another program now waits and reconnects, instead of crashing with an unhandled UnauthorizedAccessException
• Pressing the escape key shows a hint line of the available commands along the bottom of the window, restoring what was underneath when a command is chosen. --no-hint turns it off
• Key polling dropped from 100ms to 5ms, which had capped typing at about ten characters a second

Fixes #2, reported by @DavesCodeMusings.

Requires the .NET 6 runtime.