API improvement to allow fluent calls

[pm100]

A few improvements having used it myself in a non-trivial project

make all the setters return &Self. This allows fluent use

ie instead of

    textarea.set_block(
        Block::default()
            .borders(Borders::ALL)
            .title("Crossterm Minimal Example"),
    );
    textarea.set_hard_tab_indent(true);

have

    textarea.set_block(
        Block::default()
            .borders(Borders::ALL)
            .title("Crossterm Minimal Example"),
    ).set_hard_tab_indent(true)
     .set_mask_char('*');

this is common practice in rust crates with many setters

[rhysd]

Thanks for your suggestion. But I think the current setter interfaces are better because:

• It looks like builder, but TextArea is actually not a builder.
• Responsibility of setter method is setting some state. And it should not do other things. So returning nothing is the most assumed interface (especially by readers of source code).
• I don't see much benefit on this interface. It can remove a repeat of receiver. But it only saves a few key strokes.