async echo doesn't work with flush: false

[jcubic]

Issue summary

When you echo async function without flush, the output is not flushed at all

Expected behavior

flush should always output the content you echo

Steps to reproduce

Write this code:

term.echo(async () => 'Hello', { newline: false, flush: false });
term.echo(async () => ', world!', { flush: false });
term.flush();

Browser and OS

N/A

Additional notes

New devel method terminal::view_ready() fix the issue. It seems that terminal::view_ready() needs to be changed to terminal::output_ready().

[jcubic]

Also the types needs to be updated