p-inputMask Cursor-Keys "Left/Right" don't work correctly on Firefox

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Current behavior

There are several issues:

1. If no selection: It is not possible to change the cursor position by using the cursor keys.
2. With text being selected: Using the cursor keys deletes the selected part of the input string instead of unselected (native behavior).

Expected behavior

Same correct behavior like in Chrome and Edge.

• Angular version: 4.0.1

• PrimeNG version: 4.1.3

• Browser: [Firefox 55]