In iOS, the keyboard is part of the operating system and cannot be modified by apps. If you are on an iPad running iOS 13 or higher, you can "Undock" the keyboard to place it in various places on the screen. In the same way, you can split the keyboard to type with your thumbs on either side of smaller devices. This is done by tapping and holding on the keyboard key in the bottom right of the keyboard and choosing options.
You can move the keyboard back to the bottom of the screen by tapping and holding on to the keyboard key on the bottom right of the keyboard and choose "Dock" to dock the keyboard to the bottom edge of the device. If you've also split the keyboard, you can merge the keyboard and dock it. This will return the keyboard to the default position.