Add ability to zoom browser docks with Ctrl - and +

[WizardCM]

Description

Adds the ability for a user to control the zoom level of a browser dock using keyboard shortcuts.

Ctrl + 0 resets zoom, like a normal browser.

Attempts to use the same % values as browsers.

Also adds a Reset option to the context menu when zoom is not 100%.

Verify the zoom level using the following in the Inspect window:

Math.round(window.devicePixelRatio * 100);

Note that zoom level does not persist across restarts. However, even in this initial implementation it's more useful than not having it. Zoom level now persists thanks to https://github.com/obsproject/obs-browser/commit/4236b56fbe4706de17617b2fe69370b031294b29

https://user-images.githubusercontent.com/941350/226282748-f2b495bf-5d8e-4a1f-9d89-bec84a745b92.mp4

https://user-images.githubusercontent.com/941350/226282777-c6a7daef-d0d9-452a-bf1d-d9d9a093c0a6.mp4

Motivation and Context

• Accessibility.
• This is a feature that has often been requested.
• https://ideas.obsproject.com/posts/2049/zoom-tool-in-internal-browser
• Users don't often have control of the pages within their docks, and may need them zoomed in for various reasons.

How Has This Been Tested?

On Windows.

1. Press the mentioned hotkeys while a browser dock is focused.
2. Right click a browser dock with a non-100% zoom and select Reset Zoom.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.

[WizardCM]

Couple of updates since the original PR:

1. Simplified a little bit of code
2. Changed from Ctrl+* to Ctrl+0 to reset zoom (per other browsers)
3. Added Zoom In/Out menu items to the context menu
4. Thanks to a different commit pushed to master, zoom level now persists across sessions