feat(terminal): support OSC 52 to yank to system clipboard

Helper function for `App` which writes the necessary escape sequence
directly to yank the provided string.

examples/demo.zig

@@ -1,5 +1,5 @@
 const QuitText = struct {
-    const text = "Press ctrl+c to quit. Press ctrl+n to launch `vim`.";
+    const text = "Press ctrl+c to quit. Press ctrl+n to launch `vim`. Press space to yank to system clipboard.";
 
     pub fn element(this: *@This()) App.Element {
         return .{ .ptr = this, .vtable = &.{ .content = content } };
@@ -150,6 +150,12 @@ pub fn main(init: std.process.Init) !void {
             .key => |key| {
                 if (key.eql(.{ .cp = 'c', .mod = .{ .ctrl = true } })) try app.quit();
 
+                if (key.eql(.{ .cp = zterm.input.Space })) try app.yankToSystemClipboard(
+                    w,
+                    gpa,
+                    "This is a test of the OSC52 support:\n\tWith multiple lines and some special characters $?/-[]().╭─╮",
+                );
+
                 if (key.eql(.{ .cp = 'n', .mod = .{ .ctrl = true } })) {
                     try app.stop(w);
                     try w.flush();