Add PHP inspired output buffering

[jcubic]

I have an idea for a new feature for jQuery Terminal

Similar to PHP where you start buffer and then you can get the output of buffer to string.

This will allow to call exec and get the output as string.
The API can be similar to PHP.

term.ob_start();
term.exec('some command');
const output = term.ob_get_contents();
term.ob_end_clean();
// or
term.ob_end_flush();

[jcubic]

The API is"

clear_buffer();
// and
get_output_buffer();