[All platforms]: TextInputEventArgs class

Used for cross-platform use.
[WinDX]: include TextInputEventArgs.cs
[WinGL]: include TextInputEventArgs.cs
[Linux]: include TextInputEventArgs.cs
[All platforms]: new feature, InputText event
[WinDX]: TextInput implementation
Update TextInputEventArgs.cs

still me public is needed
[WinGL/Linux]: TextInput implementation
Update docs
Update docs
Merge pull request #1489 from xanather/develop

[WinGL/Llinux] + [WinDX] InputText event