fix: always show cursor on deinit

The render method always hides the cursor, and only shows it if it needs
to be shown. This has the effect that if a caller never shows the
cursor, exits the application, and the shell doesn't re-show the cursor
then we have no visible cursor.

Always show the cursor on deinit to prevent such a curse.

Fixes: #10

src/vaxis.zig

@@ -113,6 +113,8 @@ pub fn Vaxis(comptime T: type) type {
                 if (self.state.alt_screen) {
                     _ = tty.write(ctlseqs.rmcup) catch {};
                 }
+                // always show the cursor on exit
+                _ = tty.write(ctlseqs.show_cursor);
                 tty.flush() catch {};
                 tty.deinit();
             }