feat: allow free input in AutoComplete

[qrilka]

Hi @luoxiaozero here is my monkey-patched version of AutoComplete - I needed to support free input and not only selection from options.
Maybe this could be made into an option of AutoComplete, what do you think?

[qrilka]

@luoxiaozero any comments? I've also added "allow_free_input" as an option. So basically by default it almost work as a previous version. Probably the main difference is that the first option doesn't get selected by default and also options update clears up selection (the current component behaves confusingly in this respect in my opinion)

[luoxiaozero]

I think when allow_free_input is false, the previous behavior can be maintained (as long as the option is not empty, then select_option_index cannot be None)

[qrilka]

What about dropping its value to 1 when options change? That could be done behind a different option if you wish.

[luoxiaozero]

When the option changes, allow_free_input is 1 if it is false and None if it is true.

[qrilka]

Yes, like that, thanks

[qrilka]

I've also switched the option to just a boolean, not a signal. The source motivation was compile error about NotRawCallback but in principle it makes very little sense to make this option reactive.

[luoxiaozero]

Can you improve the documentation for the newly added fields? (demo_markdown/docs/auto_complete/mod.md)

[qrilka]

Should be done now

[luoxiaozero]

Thanks!