Adds zoom buttons to graph controls

[greedyAI]

Description of the changes:

• Zoom-in and zoom-out buttons have been added. When clicked or pressed, they call GraphingControl's ScaleRange function. These buttons take advantage of RepeatButton's API to allow for hold-down repeat click behavior.
• Zoom reset button has been added. When clicked or pressed, it calls GraphingControl's ResetGrid function.
• Appropriate keyboard shortcuts and light-mode styling for these buttons have also been added.

How changes were validated:

• Manual testing.

[rudyhuyn]

Good job Wei!

I've added a few comments, let me know what you think!

⚠ It seems that your Visual Studio doesn't use XAML Styler (https://marketplace.visualstudio.com/items?itemName=TeamXavalon.XAMLStyler), check that this extension is installed and enabled. Once done, save GraphingCalculator.xaml again to format the XAML code.