Fix for onServerSearch and labelRenderer

[MichalLauer]

This PR fixes issue mentioned in #664 and replaces #665.

I did not use eval(...) as suggested because I found on the internet that it might cause security issues. Because of that, I chose the window[...] approach. One notable drawback of this implementation is that the functions that will be used (passed in the onServerSearch parameter) must be defined outside of any document.ready statement.
I also updated the docs, NEWS.md and version.

Sorry if the news/version update is overboard - feel free to fix it or LMK and I'll create a new PR :)

Thanks!

[pvictor]

Thanks for this.
Can you not change version number ? Or just the 9000 part, version 0.8.2 hasn't been released on CRAN yet.
Can you put an exemple in examples/ to demonstrate how to use onServerSearch ?

[MichalLauer]

Hello @pvictor,

I added example into the examples/ folder and referenced it in the R/virtual-select.R. I also reverted back the version.
If anything else is needed, please, let me know :)

[pvictor]

That's perfect, thank you! I will release on CRAN shortly.

[MichalLauer]

Awesome, thanks for the collaboration :)