Add gestures for increase / decrease speech rate

[Qchristensen]

Is your feature request related to a problem? Please describe.

There are some situations, such as kiosks, where NVDA may be setup on a device with limited inputs. In this case, dedicated keystrokes for adjusting speech rate would be useful.

Some users may also prefer dedicated keystrokes for these functions rather than using the synth settings ring.

Describe the solution you'd like

Add a gesture for "Increase speech rate" and one for "Decrease speech rate".

In the kiosk situation, we additionally had a request to map these to USB scan codes F23 and F24. It would be worth investigating where these keys may be mapped on other devices and whether this could conflict with such a default assignment.

If this was problematic, gestures could be created without a default keystrokes.

Describe alternatives you've considered

The current workaround would be to use NVDA+control+up arrow / down arrow (or NVDA+control+shift+up arrow / down arrow). These keys increase / decrease the current synth setting ring setting. By default this adjusts speech rate. On a kiosk, these keys could be mapped to other buttons. However, in the case where the synth setting ring is able to be adjusted, it could not be guaranteed thse would adjust speech rate.

Additional context

[feerrenrut]

To summarize:

• Add scripts specifically for speech rate up/down and assign F23 & F24