ToolTip: Multiple ones possible and KeepOnHover option (#301)

* widget: Make it possible to have multiple tooltips

* widget/tooltip: Added the 'KeepOnHover' option

It'll allow the ToolTip to not be hidden when the cursor is hovering it

* _examples: Add new ToolTip option examples

For the multiple option and the KeepOnHover

Fix UT

Long press config (#293)

* Update the preferredSize calculation for tabbook to be based on the max of all tabs within it.

* Allow Long Press Duration to be set

Set VSync to true for demo

Merge pull request #243 from ebitenui/window-shift

Shift selected window to the top of the stack automatically

Merge pull request #175 from ebitenui/add-render-hook

Add render hook

Merge pull request #159 from xescugc/fg-button_text_color

widget/button: Added the ButtonTextColor.Pressed option

Merge pull request #149 from scratch85/feature/add-move-event

add move event to Widget and Button

Update Text to limit overdrawing.

Merge pull request #81 from kidk/kidk-hide-container

Added option to hide Container