Adding a search bar

[lionel42]

Hi,

I really enjoy that library !

I wanted to add a search bar widget. I tried to stay compliant with how the library works. Also tried to include the DropDown menu and TextBox functionalities to ease the implementation.

Added one py file and one md file of the doc, with an example gif where we can search a color among all the available ones in pygame.

Also fixed few things from the drop down menu:

• elements where clickable when hidden)
• selection of element occured on mouse pressed instead of mouse release (click instead of clicked)

Addition to TextBox:

• onTextChanged callback which could be useful for other application as well

Fixed imports

• Should use relative imports in package

Let me know if anything should be added/changed

[AustL]

This is an amazing addition, thank you very much!