Bind Ctrl+Numpad Plus,Minus to the font size controls (#9753)

"ctrl+numpad_plus" command now increases font size and
"ctrl+numpad_minus" command now decreases font size.

Before this only "ctrl+=" and "ctrl+-" controlled font size. Increase in
font size follows previous convention where zooms in arbitrarily large,
but decrease in font size is capped.

## Validation Steps Performed
I first ran "ctrl+=" and "ctrl+-" in my terminal to verify its behavior,
then compared that against "ctrl+numpad_plus" and "ctrl+"numpad_minus".
Both increased and decreased the font size by the same amount, and both
appeared to have a cap for how small they could get, but did not appear
to have a cap for how big they could get.

Closes #7518

(cherry picked from commit 9a276c6)

src/cascadia/TerminalSettingsModel/defaults.json

@@ -360,6 +360,8 @@
         // Visual Adjustments
         { "command": { "action": "adjustFontSize", "delta": 1 }, "keys": "ctrl+=" },
         { "command": { "action": "adjustFontSize", "delta": -1 }, "keys": "ctrl+-" },
+        { "command": { "action": "adjustFontSize", "delta": 1 }, "keys": "ctrl+numpad_plus" },
+        { "command": { "action": "adjustFontSize", "delta": -1 }, "keys": "ctrl+numpad_minus" },
         { "command": "resetFontSize", "keys": "ctrl+0" },
 
         // Other commands