* Match "mailto:" case-insensitively
* Decode mailto: param to properly handle email addresses that contain
non-ASCII characters.
* Encode email address before crafting mailto: URL so that emails that
contain '#' work properly and do not cut off URL parameters when later
generating URLs for Gmail, Outlook, etc.
* URL Encode email when generating URLs for Gmail, Outlook, etc. so
that a crafted email address cannot specify extra parameters to those
services.
* Don't append '?' to outlook email address.
* Rename encrypt to encode since "encrypt" implies hard-to-reverse
which btoa is not.
* Assign to textContent instead of innerHTML to make it obvious to
security linters that the library does not use XSS-risky patterns.
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