IAF - Initialize webview content with file URL

[evan-masseau]

Description

Previously we'd used loadDataWithBaseURL to load in our HTML template as a string and explicitly state that the "base url" of the page is klaviyo.com. It appears that this is giving us CORS errors when loading fonts from another source however.
Another option is loadData, but that appears to be limited to only loading other data resources.
The final option is loadUrl with a file:// path, which is what I'm experimenting with here. This is analogous to what the iOS SDK is doing also, and our font sheets were loading out of the box when tested there.
If this fails to load fonts reliably, I'll go back to loadDataWithBaseURL and investigate intercepting and modifying request headers instead.

Check List

• Are you changing anything with the public API?
• Are your changes backwards compatible with previous SDK Versions?
• Have you tested this change on real device?
• Have you added unit test coverage for your changes?
• Have you verified that your changes are compatible with all Android versions the SDK currently supports?

Changelog / Code Overview

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