v0.8.8

Changelog:

• Added RightClicked signal to TreeView (PR #125)
• Changed the keyboard shortcuts in EditBox and TextBox for macOS
• Added getIndexById and getIdByIndex to ListBox
• Added global setEditCursorBlinkRate function
• Added renderer properties in ComboBox for disabled state
• Added bind functions to layouts to bind to inner size
• Added getFocusedChild() and getFocusedLeaf() to Container and Gui
• Made updateTime() in Gui public and let it return whether something changed
• Picture had wrong size when loading from file with a relative size
• String to float conversion could fail since 0.8.6 when C locale was changed