fix: hide keyboard if `readonly` is added while `virtualKeyboardMode` is `off`
fix: hide keyboard if `readonly` is added while `virtualKeyboardMode` is `off`

Before, an input that was just transformed into a readonly input could have its keyboard open if `virtualKeyboardMode` is off. Also, any attempt to close it using the `hideVirtualKeyboard` command would be ignored because this [check](https://github.com/arnog/mathlive/blob/507c7d833c3abdb4f83786735b357e4b47d02d1c/src/editor-mathfield/mathfield-private.ts#L633) related to `readonly` would prevent it. To fix this, we should close the keyboard if it was open and if the input becomes a readonly input.

You can see the faulty behavior in [this](https://codepen.io/LuisMesa/pen/WNJNXVB) Codepen.

arnog/mathlive,arnog/mathlive,arnog/mathlive,arnog/mathlive