Support GPU acceleration settings on Windows & Linux

[lyimmi]

This PR adds support for webview GPU settings on Windows and Linux as discussed in issue #2264.

Windows:

• Created a new option WebviewGpuIsDisabled in windows.Options
• Modified the new webview loader to be able to accept chromium switches.
• When WebviewGpuIsDisabled set to true the webview will be initialized with the --disable-gpu switch.

Linux:

• Created a new option WebviewGpuPolicy in linux.Options.
• Created a new type WebviewGpuPolicy and three constants to be used as options.
  • WebviewGpuPolicyAlways
  • WebviewGpuPolicyOnDemand
  • WebviewGpuPolicyNever
• When the webview is set up the hardware acceleration policy is set based on the option. The default setting is WebviewGpuPolicyAlways, if it is not a valid option for the system GTK ignores it and sets an appropriate value.

Mac:
This setting is not available.

[stffabi]

LGTM. Awesome, thanks for doing this. 👍

Just two minor comments and maybe you could also already add the changelog entry.

[lyimmi]

I found a bug. If you don't set the linux options, the setup crashes. I'm fixing it now!

[lyimmi]

LGTM. Awesome, thanks for doing this. +1

Just two minor comments and maybe you could also already add the changelog entry.

Thanks @stffabi, I added the change log as well!

[stffabi]

You're welcome, thanks for doing this 🙏

[leaanthony]

This is great @lyimmi !!