Support for pre-adding domains such as "AWS account aliases"

[IAXES]

Before submitting a bug report

• I updated to the latest version of Multi-Account Container and tested if I can reproduce the issue
• I searched for existing reports to see if it hasn't already been reported

Step to reproduce

• Paste URL for your AWS account alias into the address base in Firefox.
• Attempt to use "always open this site in ..." feature of mozilla/multi-account-containers.
• Interactive UI element is not visible until after visiting the site first. However, sites like these immediately redirect to a "common" site, such as aws.amazon.com.
• It is a common use case for an individual to have multiple AWS accounts. If we were able to pre-add a site using something like AWS account aliases, it would make it a lot easier to have a single bookmark that auto-opens the Management Console sign-in page for a specific AWS account in a dedicated container/tab. However, this is not possible at this time.

Actual behavior

Interactive UI element is not available.

Expected behavior

Interactive UI element to be visible to allow adding a site prior to visiting it.

Additional informations

N/A.

Provide a copy of Troubleshooting Information page (optional)

N/A.