MSG encoding and WARC page requisites fixes

[gwiedeman]

Type of Contribution

• Bugfix (non-breaking change which fixes an issue)
• New component
• Refactoring (no functional changes)
• Documentation-only

What does this implement/fix? Explain your changes.

• Handles encoding better for MSG source files by just relying on chardet
• Improved injection of attached images in message HTML for HTML, PDF, and WARC derivatives
• Fixes issue with --external-links not including requires CSS and JS in WARC derivatives

Link to issue?

n/a

• Issue closed
• Remain open

Pull Request Checklist

Please check if your PR fulfills the following requirements:

• [] Make sure you are requesting to the develop branch. Don't PR to main!
• This contribution has sufficient documentation
• Tests for the changes have been added
• All tests pass

How has this been tested?

Operating System: Win10
Python Version: 3.9.16

Licensing

• I agree that the Mailbag Project and the University at Albany, SUNY can release this code under the MIT license.