Add shortcut to reset video capture/encoding

Reset video capture/encoding on MOD+Shift+r.

Like on device rotation, this starts a new encoding session which
produces a video stream starting by a key frame.

PR #5432 <https://github.com/Genymobile/scrcpy/pull/5432>

app/src/cli.c

@@ -1022,6 +1022,10 @@ static const struct sc_shortcut shortcuts[] = {
         .shortcuts = { "MOD+Shift+z" },
         .text = "Unpause display",
     },
+    {
+        .shortcuts = { "MOD+Shift+r" },
+        .text = "Reset video capture/encoding",
+    },
     {
         .shortcuts = { "MOD+g" },
         .text = "Resize window to 1:1 (pixel-perfect)",